It has also been shown that a different type of Coleopteran spermatogenesis exists in at least 3 families, where an odd chromosome like that in the Orthoptera occurs in place of the unequal pair.
The spermatogenesis of Syrbula and Lycosae and general considerations upon chromosome reduction and heterochromosomes.
In Part I of this series of papers, the spermatogenesis of five species belonging to four different orders of insects was considered.
I had no intention of making an extended study of the spermatogenesis of the Lepidoptera, but was interested to see if anything corresponding to the heterochromosomes of other orders could be found.
A study of the spermatogenesis of Coptocycla aurichalcea and Coptocycla guttata.
Disadvantages, if any, of completing spermatogenesis well in advance of ovulation seem to be at least partly counteracted by two annual mating periods or by mating throughout the season of activity.
Spermatogenesis is well under way by mid-June; at this time, two or three distinct layers of primary and secondary spermatocytes are present and these cells outnumber the Sertoli cells.
Sternotherus, Terrapene, and Thamnophis are alike in completing spermatogenesis late in the season and storing spermatozoa, in the seminiferous tubules or in the epididymides, during hibernation.
By the end of May, although the plumage is unchanged, the testes have diminished to the size of a haricot bean, and spermatogenesis has ceased.
The observations of Seligmann and Shattock on the relation of spermatogenesis to the development of nuptial plumage in drakes probably receive their explanation from the above facts.
In one particular case only a minute nodule of testicular tissue showing normal spermatogenesiswas found on post mortem examination attached to the intestine.
They state that on examination the testes were found to be normally developed, and spermatogenesis was in progress.
Spermatogenesis does not commence until the end of November or beginning of December.
In June and July spermatogenesis is active, and from August to October the formation of ripe spermatozoa is completed.
In one part of this organ the tubules were larger than elsewhere, and one of them exhibitedspermatogenesis in progress.
The epidermis is therefore growing while the spermatogenesis is taking place.
Footnote 148: I purposely abstain from using a more precise term, for the complicated terminology employed in spermatogenesis hardly contributes anything to the elucidation of the phenomena themselves.
As soon as we can recognize with certainty the forms of nuclear division which are ‘reducing divisions,’ the question will be settled as far as spermatogenesis is concerned.
It would be useless to seek further support for the theory by going into further details, and by critically examining the numerous observations upon spermatogenesis which have now been recorded.
This reduction must also take place in the male germ-cells, although we are not able to associate it confidently with any of the histological processes of spermatogenesis which have been hitherto observed.
On the contrary, the processes of spermatogenesis are so remarkably different from those of ovogenesis that we may expect to find that reduction is also brought about in a different manner.
Further studies on the spermatogenesis of Caloptenus femur-rubrum.
On the behavior of the nucleolus in the spermatogenesis of Periplaneta americana.
The forms selected for study have been taken from several groups of insects, and are all species whose spermatogenesis has not been previously worked out.
On the ovogenesis andspermatogenesis of Sagitta bipunctata.
The spermatogenesis of each form will be described in detail, and a general discussion of the results and their relation to the accessory chromosome and sex determination will follow.
In connection with these insect forms it is of interest to find in the spermatogenesis of Sagitta a body which stains like chromatin and behaves somewhat like the accessory chromosome.
The spermatogenesis of the aphid has been included in another paper, but a summary of results and a few figures will be given here for reference in the general discussion.
The spermatogenesis of Aphis has been fully described in another paper and will merely be briefly summarized here for the purpose of comparison with other forms.
In spermatogenesis the maturation divisions, though bearing the same relation to reduction as in oogenesis (Platner, 1889; O.
Origin of the tetrads by ring formation in the spermatogenesis of the mole-cricket (Gryllotalpa) (vom Rath).
Sutton's work on the spermatogenesis of Brachystola magna is of especial interest in this connexion.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "spermatogenesis" in a variety of sentences. We hope that you will now be able to make sentences using this word.
