242 DEVELOPMENT OF ELASMOBRANCH FISHES. 



Fig. 29 shews such aggregation ; by focusing at its optical section eleven 

 unequally large rounded bodies measuring from 0^004 0*009 mm. may be 

 distinguished. They lay as if in a multilocular gap in the germ mass, 

 which however they did not quite fill. In each of these bodies there appeared 

 another but far smaller body. These aggregations were distinguished from 

 the germ by an especially beautiful intense violet gold chloride colouration 

 of their elements. The smaller elements contained in the larger were still 

 more intensely coloured than the larger. 



He further states that these aggregations equal the segments 

 in number, and that the small bodies within the elements are 

 not always to be seen with the same distinctness. 



Oellacher's description as well as his figures of these bodies 

 leaves no doubt in my mind that they are exactly similar bodies 

 to those which I have already spoken of as nuclei, and the 

 characteristic features of which I have shortly mentioned, and 

 shall describe more fully at a later stage. A moderately full 

 description of them is to be found in my preliminary paper 1 . 



Their division into a series of separate areas each with a 

 deeply-stained body, as well as the staining of the whole of them, 

 exactly corresponds to what I have found. That each is a single 

 nucleus is quite certain, though their knobbed form might 

 occasionally lead to the view of their being divided. This 

 knobbed condition, observed by Oellacher as well as myself, 

 certainly supports the view, that they are in the act of budding 

 off fresh nuclei. Oellacher conceives, that the areas into which 

 these nuclei are divided represent a series of separate bodies 

 this according to my observations is not the case. Nuclei of the 

 same form have already been described in Nephelis, and are 

 probably not very rare. They pass by insensible gradations into 

 ordinary nuclei with numerous granules. 



One marked feature of the segmentation of the Elasmobranch 

 egg is the continuous advance of the process of segmentation 

 into the yolk and the assimilation of this into the germ by 

 the direct formation of fresh segments out of it. Into the 

 significance of this feature I intend to enter fully hereafter ; but 

 it is interesting to notice that Oellacher's descriptions point to 

 a similar feature in the segmentation of Osseous Fish. This 

 however consists chiefly in the formation of fresh segments 



1 Loc. cit. p. 415. [This Edition, p. 64.] 



