[97] EMBRYOGRAPIli' Ot^ OSSEOUS FIStlES. HT)! 



germiDal protoplasm, whicli takes it up by intussusception and api»osi- 

 tion. The coarser granules of the deutoplasm are slowly broken <lown, 

 as we saw in the case oi Alosa, and converted into the more liomogeue- 

 ous and much more linely granular and more higlily vitalized protoplasm 

 of the yelk hypoblast. 



In the very act of the mechanical dissociation of the protoplasm of 

 the egg from its deutoplasm, we have an explanation of why the nuclei 

 are attracted to the former and repelled from the latter. The first is 

 the portion of the egg which is dynamic in character, the portion iu 

 which develo})mental i)otentiality inheres; the second is in the static 

 condition of what Beale might perhaps call "formed material." This 

 attraction of the nucleus or germinative vesicle for the protoplasm of 

 the egg points to its true nature, and must be of a directive or trophic 

 character, as insisted upon by Ifauber; its office, in short, ai)pears to 

 be to direct those phenomena of protoplasmic rearrangement and con- 

 tractility, and perhaps of metabolism, which transpire during segmen- 

 tation. The rhythmical metamori)hosis of the nuclear booies into com- 

 l^lex "asters" or caryokiuetic figures, with granular lines radiating in 

 all directions through the surrounding plasma, like the pseudopods of 

 a heliozoon, would seem to indicate that something of this sort is the 

 function of a part, at least, of the nucleus. 



The first segmentation furrow, or that usually described as such, 

 which divides the germinal disk of the Teleostean ovum into two halves, 

 is, according to Ilofi'maun's investigations, not the first, but, on the 

 contrary, must be considered as the second to be developed in the order 

 of time. His researches have shown tliat a cleavage spindle is devel- 

 oped, when the germinal disk is finally marked oif from the yelk hypo- 

 blast, just after imi)regnation. The axis of this spindle also coincides 

 with the diameter of the egg. We therefore have, in this fact, the final 

 proof of the law of nuclear displcvcement, which has been pointed out 

 a little way back, and also why it is that there may be a great dissimi- 

 larity in the size of the deutoplasmic, as compared with the protoplasmic; 

 mass of germinal matter, dependent as this must be upon the amount 

 of food yelk which has been stored in the ovum during its intrafollicular 

 development. 



Inasmuch as the yelk of some ova has the form of coarse ovoidal 

 bodies, involved in a matrix of soft plasma, as iu those of Lepidosteus 

 and Aniici, for example, an ai^proach is evidently made towards the 

 condition of the stored nutrient materials in the cells of seeds. As in 

 the latter, we may call these bodies, which are said to be comi>osed of 

 ichthyine by chemists, globoids. Upon making sections of the mature 

 ovarian ova of Lepidosteus, I find that the germinative vesicle has left 

 the center of the a^g and i^assed outwards almost into contact with the 

 egg-membrane. Here the nucleus is surrounded by a mass of germinal 

 matter evidently destined to form th(^ germinal pohi of the egg. The 

 coarse globoids of the central and lower portions of the (^gg giadually 



