Notes on some Hydromedusae from the Bay ofNaples. 563 



(lue to the degeneration of the one aud the formation of anuther de 

 uovo before the first had escaped from the nucleus. 



Whether the pheuomeua herein eousidered leud further force 

 to the previous Suggestion that the vacuolatiou of the cytoplasm of 

 the eggs was probably due to changes assoeiated in some way with 

 maturation, or whether they may not rather be interpreted as ex- 

 pressions of eytoplasmic activities, or phases of metabolism similar 

 to those previously considered, may be somewhat problematieal, and 

 must so remain for the present, since my material is neither sufti- 

 ciently varied nor abundant to justify further speculations or con- 

 clusions. 



TìihulciHa niesetnhryanthenitiììi Allm. 



The conflicting accounts of the development of this hydroid 

 which have been given by earlier investigators, particularly Cia- 

 miciani, Metschnikoff (op. cit.j, and Brauer 2 led me to make some 

 observations upon living specimens, and also to collect material from 

 which to review certain of the problems involved, such as the mode 

 of cleavage, formation of the germ layers, etc. 



While from the living specimens I was able to follow the later 

 history of the embryo, its final escape from the gonophore and some 

 aspects of its independent life, it was not practicable to follow out 

 with any degree of satisfaction the details of cleavage. This was 

 done by means of sections of the gonophores made in several planes, 

 supplemented in some measure b}" the preparation of entire gono- 

 phores stained and mounted as transparent objects, much as had 

 been done in the case of living material. 



The preserved material was submitted to one of my students, 

 Miss HowLAND, who under my direction cut and stained the sections 

 and traced the phases of maturation and cleavage. and some of the 

 aspects of the later embryo. 



The difiering accounts as to the origin of the germ cells given 

 by CiAMiciAN and Weismann, aud that of Brauer seem to be rather 

 a difference of Interpretation than of fact. The germ cells have 

 been found both in the ectoderm of the peduncle of the gonophore 

 as Brauer contends and in the ectoderm and entoderm of the spadix 



» Zeit. Wiss. Z. 32. Bd. 1879 pag. 32-3. 

 - Ibid. 52. Bd. 1891 pag. 5.il. 



