ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 365 



formed elements. Other vesicles have the same appearance as these 

 last, but have a longer diameter. Others, again, have their contents 

 altered ; the epithelial layer found in the others has disappeared, the 

 cells are smaller and fill up irregularly the whole cavity of the vesicle. 

 The vesicles next extend irregularly and the spherical form may 

 gradually yield to the pyriform or tubular ; the investing layer becomes 

 thinner and the contained cells begin to break up in such a way that the 

 nucleoli become free, while the protoplasm breaks up into elongated 

 droplets. The tubes elongate, the nucleoli and their derivates collect 

 together, and the other contents form varicose filaments. 



Spermatogenesis in Man.* — Herr D. Biondi describes the develop- 

 ment of spermatozoa in Man. Before puberty the canals contain only 

 one kind of cell, round in shape, lying in a single or double row on 

 their wall, or sparsely and irregularly imbedded in a matrix towards the 

 lumen. After maturity the round cells are ariauged in pillars, in the 

 three zones which Biondi has elsewhere distinguished — primitive cells, 

 mother-cells, and, most centrally, daughter-cells. The spermatozoon is 

 developed from the nucleus of the last, and the cell-substance forms 

 imbedding debris. The next zone of cells also become transformed into 

 spermatozoa., and the peripheral cells may form mother- and daughter- 

 cells. The daughter-cells in their develoj)ment into spermatozoa exhibit 

 five stages — (1) movement of the nucleus to the peripheral pole, (2) for- 

 mation of the middle portion, (3) formation of the head, (4) formation 

 of the tail, (5) liberation. The spermatozoa are expelled, along with 

 the basal cell, by the expansion of neighbouring cells. The epithelial 

 cells of Sertoli, the supporting cells of Merkel, the spermatoblasts of 

 von Ebner, are artificial products, resulting from the collocation of 

 spermatozoa, protoplasmic debris, and basal cells. ' 



Import of Polar Globules.f — Herr G. Platner notes an important 

 histological fact, which naust be considered in the interpretation of polar 

 globules. In ordinary cell-division, the nucleus after dividing returns 

 from aster to coil, and thence to reticulum and rest. There are, however, 

 two exceptions. It is well known that in the formation of the second polar 

 globule the resting-stage is skipped. Tiie second polar spindle arises 

 directly from the internal daughter-plate of the first polar spindle. The 

 half of the nucleus which goes off in the first polar body frequently 

 behaves like the half which remains. The second exception seems to be 

 less known ; it occurs in the last division of the sperm-forming cells. 

 Here again the resting-stage is skipped ; from the daughter-plate of the 

 second last division the final division- spindle arises directly. The 

 overleaping of the resting-stage in spermatogenesis was studied by 

 Platner in Lepidoptera and Pulmonata. He correlates the two parallel 

 and exceptional facts ; in both cases there is a reduction by division of 

 the nuclear mass previous to the final differentiation of female pronucleus 

 in the one case, of spermatozoon nucleus in the other. 



In the testes of Lepidoptera there are at first only small cells, which 

 divide frequently and regularly. Suddenly large cells appear, which 

 Platner compares to ova. These divide twice as ova do in forming 

 polar globules. This fact adds a new precision to the comparison 

 between the male and female elements. Furthermore, if the fact 



" JB. Schles. Ges., Ixv. (1888) pp. 35-8. 

 t Biol. Centralbl., viii. (1889) pp. 718-20. 



