146 A. RICHARDS. 



cells to form the vitellarium and shell gland. It lies posterior 

 to the part which becomes the ovary arising from a group of cells 

 branched off from the middle portion of the anlage that portion 

 which becomes the oviduct. The medullary portion develops 

 first becoming the- shell gland; from the periphery of this newly 

 differentiated anlage are proliferated cells which become the 

 vitellarium proper. 



The morphological relations of this organ and the ovary suggest 

 that the vitellaria are fundamentally ova specialized along an- 

 other line than reproduction. This view, I think, is clearly 

 supported by the evidence. 1 I have, therefore, endeavored to 

 find a parallel in their development; it is not, however, a very 

 close one. They agree in that they early pass through their 

 division stages and do not proliferate during the production of 

 yolk. (I have seen only a single case of division, and that not 

 clear, in a nucleus of that period.) They differ in that the oogo- 

 nial nuclei continue to increase in size long after the vitellarium 

 nuclei have reached their full growth and the former are always 

 more chromatic than the latter. The vitellaria never go through 

 the synapsis stage and the method of yolk formation is unlike 

 that of the oogonia. Small spherules which fuse with one another 

 are formed in the cytoplasm. The mass thus arising grows larger 

 pushing the nucleus to one side. The completed cell looks not 

 unlike a fat cell of the "signet ring" type. 



Like the ovary the vitellarium at the time when cell multiplica- 

 tion stops develops a membrane separating it from the other 

 organs of the complex. Previous to this stage the cytoplasmic 

 boundaries have not been as clearly defined as those of the other 

 cells of the primary anlage, but now they become quite distinct 

 and the cells more dense. The nuclei develop more chromatin, 

 not in the form of a spireme as in the case of the ova, but as 

 enlarged granules giving to the nucleus the appearance of several 

 nucleoli. Sometimes strands may be seen extending from the 

 nucleoli out to the periphery where the yolk masses are forming. 



The further history of the cells of the vitellarium is of great 

 interest from the standpoint of the histology of secretion but is 

 outside the scope of the present problem. 



!Cf. Child, 'o-jb, p. 113. 



