The germ-cells. . 637 



III. The Germ-Cells of Embryos of 10—12 mm. 



Many such embryos have been closely examined, and, though no 

 two are exactly alike in detailed characters, the sum-total always 

 comes out to much the same result. Three only need concern us 

 here. They are Baja hatis Nos. 402, 410 and 419. 



Characters. Of the characters of embryos of this period two 

 may be named. There are from 90 to 106 mesoblastic somites and 

 five branchial pouches. Of the latter either two or three are open 

 to the exterior. Such embryos, therefore, correspond to those of 

 Pristiurus with 55 to 70 somites. 



B. hatis No. 410 (10 mm) was preserved in Flemming's solution. 

 The stain was borax- carmine. Although the yolk-plates are only 

 tinged brown and rarely blackened, the germ-cells stand out very 

 clearly. This is at least as much due to their clear glassy proto- 

 plasm as to the contained yolk. 



The figures from embryo No. 410 are Figs. 10, 11, 13, 16 and 19. 



The germinal ridge or nidus is not yet represented as a distinct 

 structure, and, therefore, at first sight one is at a loss to say what 

 should and what should not be regarded as a normally placed germ- 

 cell. In my tabulation of them a rather broad view of the normal 

 germ-region or nidus has been taken. All those germ-cells, which 

 lay anywhere near the future genital region, were considered as 

 normally placed. 



It has all along been far from my mind to exaggerate in the 

 very least the abnormal situations of germ-cells; on the contrary, in 

 order not to minimise the eiîect of undoubted finds, the tendency has 

 been to diminish or depreciate somewhat the observed abnormality. 



Nature herself, however, so augments the abnormalities of their 

 occurrence, that these, while they have never ceased to be remarkable 

 and to excite wonder, have transferred the anomaly to another sphere, 

 namely, to what we have hitherto deemed to be the rule. It is what 

 one, what Rabl in his recent work, terms the rule, which is unnatural 

 and irregular, and not the conditions seen in my embryos ! 



In embryo No. 410 those germ-cells were counted as normal in 

 position, which were near the future, germinal bed, and also those 

 within the myotomes and mesonephric tubules. In the two latter 

 there were very few — hardly any in fact. As normal were also in- 

 cluded those within, i. e., to the inner side of, the splanchnopleure. 



The enumeration was difficult, for the germ-cells were often very 



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