296 ALLEN. [VOL. I. 



very evident. All this would indicate that they were glandu- 

 lar in function. They are largest and most numerous in the 

 peduncle and occasionally one is found in the manubrium, but 

 such cases are rare. It would be impossible to distinguish a 

 section through the peduncle of a male head from that of a 

 female, as these cells are equally conspicuous in both. PI. I, 

 Fig. 8, shows a number of these glands, one of which resem- 

 bles an egg, but other sections through the same peduncle 

 show that it is really in contact with the supporting lamella. 



In the younger stages of development the manubrium of the 

 female appears to consist entirely of endoderm, but when the 

 gonophore is fully mature and the primitive ova have disap- 

 peared, a thin layer of ectoderm is found to be present. It 

 consists of a single layer of much flattened cells with smaller 

 nuclei than those of the germ-tissue cells from which they are 

 derived. 



Development of tJie Ovnvi. 



The primitive egg cells make up the large mass of tissue 

 lying between the manubrium and the inner wall of the bell. 

 They are packed closely together, so that the outlines of the 

 cells are more or less irregular. The nuclei are large and 

 spherical and contain a prominent nucleolus which takes a very 

 deep stain. The mass of protoplasm surrounding each nucleus 

 is small, and the cell boundaries are very indistinct (PI. I, 



Fig. 4)- 



As the gonophore grows older the nuclei of the germinal 

 tissue become much larger and more prominent, the mass of 

 protoplasm surrounding them increases in bulk, and the cell 

 boundaries become more clearly denned. At this stage the 

 nuclei appear as very large spheres, with the chromatin fibers 

 arranged in a sort of network around the periphery. Within 

 the layer of chromatin is a colorless mass, near the center of 

 which lies the nucleus suspended by four or five slender threads, 

 which run out to the layer of chromatin. These threads take 

 a fainter stain than the chromatin fibers and are only visible in 

 especially well prepared specimens. 



The nucleolus is usually spherical or slightly elongated, 



