730 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Spermatogenesis of Mammalia.* — Herr C. Benda communicates a full 

 report of his recent researches on the process of spermatogenesis in mammals. 

 His investigation is based upon the ox, the rabbit, the guinea-pig, the boar, 

 the rat, the mouse, the dog, and the cat, 



(1) The seminal canals of Mammalia include two functionally different 

 elements — the mother-cells (Stammzellen) with their derivatives, and the 

 basal-cells (Fusszellen). (2) The process of spermatogenesis is accom- 

 plished in four stages — (a) Multiplication of mother-cells ; (6) formation of 

 sperm-cells (Samenzellen) from some of the mother-cells ; (c) copulation 

 between the basal-cells and the former ; (^cT) modification of the thus united 

 sperm-cells into spermatozoa. (3) All the four acts occur by successive 

 displacement (schubweise). 



(4) The multiplication of mother-cells occurs by indirect cell-divisions 

 in the most external cellular layer of the seminal canal. (5) The formation 

 of a row of sperm-cells is effected by a preparative alteration in the posi- 

 tion of the mother-cells. The latter multiply by indirect division in the 

 inner layers of the canal, and some of the results form reserve mother-cells. 



(6) After the perfecting of a generation of sperm-cells, the basal-cells in 

 the outermost zone conjugate with them, each basal-cell uniting with a 

 number of sperm-cells. (7) Contemporaneously with or immediately after 

 the occurrence of this conjugation the sperm-cells begin to be modified 

 into spermatozoa. (8) The nucleus forms the various parts ; the cellular 

 body is dissolved. (9) The portion of the nucleus nearer the point of 

 copulation forms the head, the reverse the tail. (10) During their entire 

 modification the sperm-cells remain in organic connection with the basal- 

 cell, and form by active and passive modifications of the latter a bundle of 

 spermatozoa. (11) They are expelled as they actively or passively lose 

 their connection with the basal-cell, and are pressed out laterally by the 

 proliferation of adjacent elements. 



(12) The various steps occur regularly in each part of the tubule, so 

 that certain events in successive rows of seminiferous cells always coincide. 

 Thus the close of a period of modification coincides with that of the multi- 

 plication of sperm-cells ; the beginning of the former occurs at the same 

 time as the preparative alterations of the mother-cells ; these preparative 

 changes always occupy the same time as two periods of modification ; two 

 rows of sperm-cells are always in process at the same time ; the close of each 

 process of modification is contemporaneous with the perfecting of a genera- 

 tion of sperm-cells, so that at the end of modification the material for the 

 next period is already in progress. (13) In each portion of a seminal tubule 

 it is therefore possible to have a periodic secretion of spermatozoa, and an 

 unbroken succession. (14) The secretory periods in the different portions 

 of the tubule do not coincide. (15) By a regular alternation of the secretory 

 periods in the different parts of the tubules there is a possibility for con- 

 tinuous secretion throughout the mammalian testis. 



Significance of the Yolk in Osseous Fishes.f — Mr. E. E. Prince is of 

 opinion that the yolk of the Teleostean egg is accessory, an appendage not 

 directly contributing to the building up of the tissues, but mainly serving 

 to furnish pabulum to the delicate and rudimentary embryo on emerging 

 from the egg; the presence of large oleaginous spheres in the yolk 

 confirms this view, for these globules appear to have no intimate connection 

 with development. 



If this view be correct, the germ is discoblastic, and the invaginated 



* Arch. f. Mikr. Anat., xxx. (1887) pp. 49-110 (3 pis.), 

 t Ann. and Mag. Nat. Hist., xix. (1887) pp. 1-8 (1 pi.). 



