HISTOLOGY AND DEVELOPMENT OF MYRIOTHELA PHBYGIA. 515 



In the further history of the gonophore I am only concerned 

 with one point, namely, the fate of the primitive germ-cells. 

 I entirely agree with Allmann that in their earliest history it 

 is impossible to distinguish between male and female gono- 

 phores. Position does not help one, for, as has been recognised 

 before, both male and female elements are produced on the 

 same blastostyle, and to a certain extent indiscriminately, the 

 same transverse section frequently passing through both male 

 and female gonophores. Very soon, however, the male gono- 

 phores become distinguished by the rapid proliferation of their 

 generative elements. 



In the female gonophore at some period, often relatively late, 

 two or three of the generative cells become larger and more 

 prominent than the others. The period at which this happens 

 does not appear to be fixed ; and whatever factor it may be, 

 whether something inherent or accidental, that determines 

 which of these struggling cells shall obtain the mastery and eat 

 up its fellows, it sometimes does not come into play until the 

 gonophore has become a well-formed structure. But it is quite 

 late in the history of the gonophore, when that structure is 

 large and already swollen with yolk, before these two, three 

 or four cells, which, so to speak, have succeeded in attaining to 

 the final heat, decide who is the winner. 



In the facts which have been set down above with regard to 

 the structure of the ectoderm of the blastostyles, and the for- 

 mation of the gonophores, two main points appear to me to be 

 of special significance. These are (1) that the gonophore 

 appears to be a curiously modified bud, and (2) that the gene- 

 rative elements pre-exist as free cells having lodgment in the 

 tissues of the adult, and only travel into the abortive bud, 

 which is their place of final development. 



maternal tissues, and not to the gonophore bud. They are, therefore, not 

 included in the above statement. 



