STINGING-CELLS IN CRASPEDOTE MEDUSA. 773 



erroneous, and states that carefully cut series of sections of 

 developing medusa-buds show that a double-walled cup of 

 endoderm is not present at any stage; moreover, the four 

 radial canals arise from four unconnected pouches of endo- 

 derm which grow out separately, although simultaneously, 

 from the coeleuteron of the bud, and are completely indepen- 

 dent of the entocodon. The endoderm lamella is formed 

 later by the lateral extensions of the solid edges of these 

 pouches, which finally fuse with one another. Again, an 

 invagination of the superficial ectoderm does not take place 

 and the forecast of the velum is present at a quite early 

 stage, and is then represented by the flattened apex of the 

 bud, where the superficial ectoderm and the distal wall of the 

 entocodon come into contact with one another. 



Goette's paper has not received (at any rate in this country) 

 the attention which so important a communication deserved, 

 and the only confirmation of his results is that of his pupil, 

 Walter Richter (13), who, acting on his professor's advice, 

 worked out the development of the gonophores in Rhizo- 

 phora, Physalia, and other Siphonophora and described a 

 similar origin for these structures in this division of the 

 Hydromedusas. 



In my account of the anatomy of the hydroid stage of 

 Moerisia I did not go into this subject with any detail, but 

 merely stated that the development of the medusa-buds 

 seemed quite typical, the growth of the cavity in the ento- 

 codon causing the approximation of the endodermal walls of 

 the bud. 



The examination of a large series of sections during my 

 mvestigation of the origin of the nematocysts has shown me 

 that this statement was erroneous, and that the development 

 of the medusa of this form agrees very closely with that of 

 Podocoryne carnea as desribed by Goette. My error, 

 like that of other writers on the same subject before Goette, 

 was due to the use of optical sections, and partly to the 

 examination of single sections of the buds instead of complete 

 series. 



