Transverse section through the procephalic lobes of an embryo of the same age.
Section through the procephalic lobes of an embryo of the same age.
Near the opposite end of the blastoderm is a white area, which is probably the rudiment of the procephalic lobe.
But the protocerebrum contains the ganglia of the ocular segment in addition to those of the procephalic lobes.
It is now ascertained that the procephalic lobes consist of three divisions, so that the head must certainly be formed from at least six segments.
Beneath the procephalic lobes the mesoblast has, in most respects, a constitution similar to that of a mesoblastic somite in the trunk.
The epiblast of the procephalic lobes is a thick layer several cells deep, but without any trace of a separation of the ganglionic portion from the epidermis.
The six segments behind the procephalic lobes are the six largest, and each of them bears two prominent appendages.
There is a very distinctly bilobed procephalic region (pr.
In my earliest stage of the third period there is present, as has already been stated, a procephalic lobe, and an indistinct and not very prominent caudal portion, and about three segments between the two.
The caudal lobe, though less broad than the procephalic lobe, is still a widish structure.
There can be no doubt that the line connecting the cumulus with the triangular area is the future long axis of the embryo, and the white area is, without doubt, the procephalic lobe of Balbiani.
The space between the cumulus and the procephalic lobe grows larger, so that the latter gradually travels towards the dorsal surface and finally vanishes.
The two foremost, ch and pd (especially the first), of these are far less distinct than the remainder, and the first segment is very indistinctly separated from the procephalic lobe.
There is certainly, as is very well shewn in my longitudinal sections, a thickening of the blastoderm in the caudal region, though it is not so prominent in surface views as the procephalic lobe.
The caudal and procephalic lobes are very similar in appearance, but theprocephalic lobe is slightly the wider of the two.
He believes however that the anterior segment forms the procephalic lobes, the posterior probably the telson and five adjoining caudal segments, and the middle one the remainder of the body.
The mouth appears as a slit-like opening between and below the procephalic lobes.
Not only is a pair of mesoblastic somites formed for each segment of the body, but also for the procephalic lobes (fig.
In succeeding stages the anterior of the three parts is clearly marked out as the procephalic lobe, and soon becomes somewhat broader.
These two appendages next turn inwards towards the mouth, and their bases become gradually closed over by two processes of the procephalic region (fig.
The position of the supra-oesophageal ganglia on the ventral side of the procephalic lobes is the same as that in other Tracheata.
By the time that twelve segments are definitely formed, the procephalic region is distinctly bilobed, and in the median groove extending along it the stomodaeum has become formed (fig.
The embryological characters of the procephalic lobes, of the limbs and claws, place however this conclusion beyond the reach of scepticism.
The procephalic lobes resemble those of the Arthropoda generally, and are unlike the prae-oral lobe of Chaetopods or Discophora.
The supra-oesophageal ganglia are formed from the procephalic lobes.
By a continuous elongation the ventral plate comes to form a nearly complete equatorial ring round the ovum, the procephalic and caudal lobes being only separated by a very narrow space, the undeveloped dorsal region of the embryo.
In the procephalic lobe there is a well-developed section of the body cavity, which lies dorsal to and in front of the rudiment of the supra-oesophageal ganglia.
Each procephaliclobe is now marked by a deep semicircular groove.
The supra-oesophageal ganglia are stated to be developed quite simply as a pair of thickenings of the procephalic lobes, but whether they are from the first continuous with the ventral cord does not appear to have been determined.
The supraoesophageal ganglia arise as an unpaired median thickening of the procephalic lobe.
The supraoesophageal ganglia are formed as two independent thickenings of the procephalic lobes (fig.
The supraoesophageal ganglia of these animals are formed in the embryo from two thickened patches of the epiblast of the procephalic lobes.
In the Isopoda supraoesophageal ganglia are stated to arise as thickenings of the procephalic lobes, which become eventually detached from the epidermis.
There is first formed a pair of pits on the procephalic lobes, which become very deep during the Nauplius stage, and are continuous with a pair of epiblastic ridges which pass round the mouth, and join the ventral cords just described.
The procephalic lobes, from which a great part of the head, including the antennæ, is developed, are often counted as an additional segment.
The foremost segment soon enlarges beyond the rest, and becomes divided by a median groove into two “procephalic lobes.
The rudimentary thorax presents traces of a division into three segments; and the dorso-lateral margins of the cephalic blastoderm, behind the procephalic lobes, have a sinuous margin.
This portion is divided by a median fissure into two lobes, which play an important part in the development of the head, and will be termed the 'procephalic lobes.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "procephalic" in a variety of sentences. We hope that you will now be able to make sentences using this word.
