W. K. BEOOKS ON THE GENUS SALPA. 275 



end are often to be seen in the protoplasm. One of them is shown near 

 the middle of the left side of the lowest blastomere in Fig. 1. Besides 

 these well marked and characteristic nuclei, the protoplasm of the blasto- 

 meres contains a number of vaguely denned indefinite bodies which 

 stain diffusely and uniformly in haematoxylin. Some of these are 

 almost invisible, while others retain enough of the character of follicular 

 nuclei to show that they enter the protoplasm of the blastomeres in great 

 numbers, and are gradually dissolved and lost in its substance. The fate 

 of those which are not brought by their lines of motion into contact with 

 the blastomeres is somewhat different. They lose their elongated shape 

 and become spherical, their chromatin becomes diffused and they finally 

 grow indefinite, and appear to break up at last into separate granules. 



These phenomena seem to me to admit of only one interpretation. 

 Some of the nuclei penetrate the substance of the blastomeres and are 

 digested, while others degenerate and go to pieces among the blasto- 

 meres to supply them with food. During the early stages in the history 

 of the blastomeres, most of the assimilated food seems to be converted 

 into chromatin, for comparison of Figs. 1, 2, 3 and 4 shows that while 

 the protoplasm of the blastomeres remains transparent, the nuclear net. 

 work becomes more and more conspicuous, while the central nucleolus 

 increases in size. As the blastomeres multiply and become smaller, 

 Figs. 5, 6 and 8, their protoplasm also gradually becomes granular and 

 opaque, so that they are distinguished from the surrounding follicle 

 cells, both by their granular structure and by the nucleolus and chro- 

 matic network, as is shown in Fig. 9, where 8 and x are follicle cells, and 

 b and a endodermal and ectodermal blastomeres. 



So far as I am aware, no one except Salensky has noted the exist- 

 ence of the follicular nuclei in the protoplasm of the blastomeres, and 

 his interpretation of them is directly opposed to mine, as he sees in them 

 evidence of the degeneration of the blastomeres. 



He believes that the tissues of the embryo are formed out of the 

 follicle cells (gonoblasts, kalymmocytes), and that the blastomeres are 

 used up as food, and on page 340 (5), he gives the following statement of 

 his view: "All the organs of the body of the embryo are built up from 

 gonoblasts, while the blastomeres pass more and more into the back- 

 ground and play scarcely any part in the formation of the organs. 

 Development begins according to the general type of sexual reproduc- 

 tion, but it soon passes over into the asexual. Since the construction of 

 the salpa-embryo proceeds from those elements which are not derived 



