20 SUMMAKY OF CURRENT RESEARCHES RELATING TO 



been observed in Dytiscid^e by Ballowitz and by Auerbach, and in 

 Didelphys by Selenka. 



So-called Conjugation of Spermatozoa and Sertoli's Cells.* — K. 

 Tellyesniczky discusses, with particular reference to the rat, the factors 

 that go to the formation of sperm-bundles, and the so-called conjugation 

 of spermatozoa and Sertoli's cells. The plasma of the sperms coalesces 

 with that of the Sertoli-elements, but this is a merely mechanical fusion 

 due to limited space. There is no special conjugation-process. The 

 general conclusion of the author's study is that mechanical factors — the 

 growth, division, crowding, and shunting of the sperm-cells — are quite 

 sufficient to account for the formation of bundles without any theory of 

 taxis or tropisms. 



Heteromorphous Spermatozoa in Rana muta.f — E. Ballowitz 

 notes the regular occurrence of numerous markedly heteromorphous 

 spermatozoa in the mature seminal fluid of this grass-frog ( = i?. tem- 

 poraria). The atypical spermatozoa are marked by the form of the head 

 and by their movements. The outgrowth of the nucleus and apical 

 piece into an elongated structure has been suppressed, while the tail has 

 its normal development. The case is not comparable to the dimorphism 

 in Prosobranchs, and there is no question of the atypical forms being 

 immature. 



Theory of Maturation.:]: — ]\I. Kuckuck maintains that the cause of 

 maturation-divisions is to be found in the dynamic dissimilarity of the 

 maternal and paternal components in the " hermaphrodite " sex-cells. 

 In the mother-egg-cell the nucleus of maternal origin is more " energetic " 

 than that of paternal origin, and conversely for the mother-sperm-cell. 

 Only after maturation-divisions is the sexual affinity pronounced — by 

 the separation of paternal and maternal chromosomes in the second 

 maturation-division, which is therefore not only a reducing division, but 

 a segregation-division. The mechanism is due to differences in electric 

 potential, and an elaborate theory is worked out. The fully functional 

 spermatozoa are those with wholly paternal nucleus ; those with maternal 

 nucleus are comparable to the second polar bodies (with paternal nucleus) 

 — rudimentary sex-elements deficient in energy. 



Origin of the Sertoli or Foot-cells of the Testis.§— C. E. Walker 

 and Alice L. Embleton conclude that the foot-cells of the testis, and 

 the cells foi'ming the walls of the tubules or pockets, have immediately 

 common ancestors ; and that if these cells are not identical with certain 

 stages in the series of leucocytic generations, they are derived from cells 

 that were identical not more than two or three generations before. 



Observations on Life-history of Leucocytes. || — C.E. Walker points 

 out that there are remarkable points of similarity between the life- 

 histories of leucocytes and those cells in plants which, though reduced, 

 never become converted into sexual elements. This comparison is 



* Arch. Mikr. Anat., Isviii. (1906) pp. 540-72 (1 pi.). 

 t Zool. Anzeig., xxx. (1906) pp. 730-7 (11 figs.). 

 X Tom. cit., pp. 345-57 (12 figs.). 



§ Proc. Eov. Soc. London, Series B, Ixxviii. No. B522 (1906) pp. 50-52 (2 pis. 

 and 1 fig.). ' l| Tom. cit., pp. 53-9 (4 pis.). 



