DEVELOPMENT OF THE EGG OF CLAVA LEPTOSTYLA. 215 



this opinion. Indeed, as pointed out before, the extremely er- 

 ratic and anomalous behavior of these eggs during cleavage would 

 seem to render extremely difficult, if not impossible, any prede- 

 termining factors in either cytoplasm or nucleus, whose influence 

 could be maintained during the varying and indeterminate process 

 of development. While we may readily admit that, as Conklin 

 has suggested, there must be factors present which determine 

 that the egg shall develop into a Pcnnaria, still this does not 

 compel the conclusion that therefore they must be definitely 

 localized. It is simply a matter of heredity ; and if it be true as 

 generally contended that this is a problem of chromosomes ; and 

 if, as I have shown in the case of both Pennaria and Eudendriuin, 

 the chromatin may be more or less dispersed throughout the 

 entire cytoplasm during maturation and early cleavage, then 

 definite localization in one or the other is not involved in Conklin's 

 sense of the term. However, it must be regarded as a question 

 of fact, and so far as evidence exists in the present case it would 

 seem to be opposed to the theory of localization. 



During June and July of the past summer I carefully studied 

 the living eggs of Clava, and with this point still clearly before 

 me. As pointed out in an earlier section, the eggs originate in 

 the entoderm of the gonophore, and grow by direct nutrition 

 derived from the cells of that tissue. A study of the eggs in 

 various stages of growth revealed the appearance at a certain 

 stage of development of a delicate, bluish pigment, which grad- 

 ually accumulated in amount as the eggs approached maturity. 

 This was carefully observed in the living specimens and has since 

 been studied in sections after a variety of fixations. At first the 

 pigment makes its appearance in the immediate region of the 

 nucleus, about the time that body takes its place at the outer 

 periphery of the egg. This is shown in Fig. I, Plate I. From 

 the nuclear region the pigment extends as a crescentic disc out- 

 ward, forming later a peripheral zone which finally extends over 

 the entire egg, though this rarely occurs until cleavage has made 

 some progress. 



An interesting fact observed in this connection was that the 

 amount, or at any rate the color-intensity, of the pigment differed 

 considerably in different specimens. This was particularly the 



