

160 Dr. C. Chun on the Siphonophora. 



This also explains why in fishing we often meet with the 

 calyces of Monophyes destitute of all appendages, besides the 

 isolated sexual calyces of the Eudoxice. After its separation 

 the calyx of the Muggicea grows rapidly, and attains about 

 three times the size of the Mo7iophyes-c&\yx. But it is not 

 only upon the almost fully developed calyx of the Muggicea 

 just described that the connexion of the two generations may 

 be demonstrated, but even in the insignificant globular bud 

 on close examination the course of the vessels characteristic of 

 the developed calyx already makes its appearance distinctly. 

 A glance at fig. 5 shows how the tissues of the stem take 

 part in the construction of the bud, how the ectoderm passes 

 continuously into the external wall of the bud (the umbrella 

 was even previously formed by an ectodermal invagination), 

 while the endoderm produces, by a dilatation, the first traces 

 of the fluid-receptacle and the vascular lamella, in the latter 

 of which the vessels take the course typical of the developed 

 Muggicea. 



The fact that by the side of a small cap-shaped nectocalyx a 

 second one so totally different in form and size is budded forth, 

 destined to separate from and perform the same function as 

 the primary calyx, is unique among the Coelenterata. We 

 find indeed on the stem of the Siphonophora the most various 

 polymorphic appendages ; but the different form is always 

 determined by a different function ; the medusiform locomo- 

 tive is of different construction from the medusiform genital 

 nectocalyx budded from the same stock. But how are we to 

 explain the fact that in this case two calyces intrusted with 

 the same function, namely the locomotion of the stock, acquire 

 such a different habit ? 1 know of no other answer to give to 

 this question than that the small cap-shaped Monophyes-c&lyx 

 suffices for the transportation of the single stomachal sac with 

 the tentacle, but that with the elongation of the stem and the 

 increase of the individual groups it becomes necessary, by a 

 larger and more slender calyx, which can cut through the 

 water easily, to weaken the resistance which is opposed to 

 rapid locomotion by the long drawn-out trailing stem^with 

 its appendages* That the Diphyid-like calyx of the Muggicea 

 fulfils such requirements will be the experience of any one 

 who attempts to take out the little stock as it shoots through 

 the water w r ith the rapidity of an arrow. 



But although I believe that I have proved as an esta- 

 blished fact that the cyclical course of development of these 

 lowest Siphonophora consists of three generations, scientific 

 method requires the proof that Monophyes prima rdialis really 

 originates from the ova of the Euchxia budded off from the 



