OF THE VERTEBRATE OVARY. 581 



protoplastic network of the earlier stages is still present, and 

 serves to hold together the constituents of the yolk. In the 

 cortical layer of nearly ripe ova, the yolk has a somewhat differ- 

 ent character to that which it exhibits in the deeper layers, chiefly 

 owing to the presence of certain delicate granular (in hardened 

 specimens) bodies, whose nature I do not understand, and to 

 special yolk spheres rather larger than the ordinary, provided 

 with numerous smaller spherules in their interior, which are 

 probably destined in the course of time to become free and to 

 form ordinary yolk spheres. 



The mode of formation of the yolk spheres above described 

 appears to me to be the normal, and possibly the only one. 

 Certain peculiar structures have, however, come under my notice, 

 which may perhaps be connected with the formation of the yolk. 

 One of these resembles the bodies described by Eimer 1 as 

 " Dotterschorfe." I have only met these bodies in a single 

 instance in ova of O'6 mm., from the ovary (in active growth) 

 of a specimen of Scy. canicula 23 inches in length. In this 

 instance they consisted of homogeneous clear bodies (not bounded 

 by any membrane) of somewhat irregular shape, though usually 

 more or less oval, and rarely more than O'O2 mm. in their longest 

 diameter. They were very numerous in the peripheral layer of 

 the ovum, but quite absent in the centre, and also not found 

 outside the ovum (as they appear to be in Reptilia). Yolk 

 granules formed in the normal way, and staining deeply by 

 osmic acid, were present, but the " Dotterschorfe " presented 

 a marked contrast to the remainder of the ovum, in being 

 absolutely unstained by osmic acid, and indeed they appeared 

 more like a modified form of vacuole than any definite body. 

 Their general appearance in Scyllium may be gathered from 

 Eimer's figure 8, PI. 11, though they were much more numerous 

 than represented in that figure, and confined to the periphery of 

 the ovum. 



Dr Eimer describes a much earlier condition of these 

 structures, in which they form a clear shell enclosing a 

 central dark nucleus. This stage I have not met with, nor can 

 I see any grounds for connecting these bodies with the formation 



1 " Untersuchung iiber die Eier d. Reptilian," Archiv f. mikros. Anat. Vol. VIII. 



