THE MALE-CELL OR SPERMATOZOON. 



107 



Difficulties become thick, however, when we inquire into .the division of the 

 mother-sperm-cell or spermatogonium, and it is here that the observations of 

 recognized authorities so much disagree. Accepting the results of competent 

 observers, we have elsewhere endeavored to rationalize and unify the con- 

 flicting observations by comparing the different modes of spermatogenesis with 

 the different forms of ovum-segmentation. It has been already incidentally 

 noticed that the egg-cell may divide wholly and equally, or unequally, or only 

 very partially, or round a central core. Just in the same way the mother-sperm- 

 cells may divide into a uniform ballof cells, or only at one pole, or only at the 

 periphery round a central residue. Balfour and others had hinted at this corn- 



s' 



C 



A' 



Fig. 30. — Comparison of Spermatogenesis and Ovum Segmentation. 



Explanation. — The first line, A-E, exhibits types of ovum segmentation: — A, regular morula; B, 

 unequal segmentation, for example, in some Mollusks; C, centrolecithal or peripheral type, for 

 example, in a shrimp Peneus ; D, partial segmentation ; E, the same, with the cells less markedly 

 defined off from the yelk. 



In the next two lines various types of spermatogenesis are collated with the above to illustrate the 

 parallelism: — A' and A", morula type, as in Sponge, Turbellarian, Spider, &c; B' and B", where the 

 division is unequal, and one large nutritive cell is seen (Plagiostome fishes, Von la Valette St. George) ; 

 C and C", after Blomfield, Jensen, &c, showing central cytophoral or blastophoral nutritive portion; D' 

 and D", sperm-blastoderm, with a few formative cells on large nutritive blastophore, after Gilson, &c; E' 

 <jnd E", the same, with the sperm-cells less definitely separated off, after Von Ebner and his followers. 



parison in the use of terms like sperm-morula; and Herrmann had also con- 

 cluded, "that the division of the male ovule into a series of generations of 

 daughter-cells, is a phenomenon comparable to that exhibited by the ovum in 

 the formation of the blastoderm. ... It seems, then, more important to deter- 

 mine exactly the mechanism of division than to give a particular name to each 

 stage of segmentation." 



Although this interpretation of spermatogenesis by collating it with ovum- 

 segmentation appears to Minot " a fanciful comparison," in favor of which he 

 is "unable to recognize any evidence," neither the initial homology between 

 the mother-sperm-cell and ovum with which we start, nor the striking parallelism 



