162 Dr. C. Chun on the Siphonophora. 



and already begins to perform pumping movements, although 

 it is still covered with delicate vibratile cilia, A large 

 swelling, chiefly composed of the juicy endodermic cells, is 

 appended to it laterally, which passes over continuously into 

 the still-closed stomachal sac. The latter is of an intensely 

 red colour, and displays a central cavity free from juicy cells. 

 At its base protrude the numerous fungus-like buds of the 

 rudimentary tentacle. The juicy cells are now absorbed, the 

 tentacle with its urticating batteries elongates, and finally the 

 mouth of the stomachal sac breaks through ; and at the close 

 of the third day the larva acquires a form which exactly 

 agrees with that of the youngest stages of Monophyes captured 



in 



the 



open. 



The proof being thus furnished that the fecundated ovum of 

 Eudoxia Eschscholtzii develops into Monophyes primordialis, 

 we have to note the following stages in the course of develop- 

 ment of the latter : 



1. The planula. 



2. The embryo with the bud-rudiments of the nectocalyx 



and tentacle. 

 8. Monophyes primordialis. 



4. Muggicea Kochii. 



5. Eudoxia Eschscholtzii. 



cLi 



II. The Relationships of the Siphonophora. 



By the demonstration that three generations intervene in 

 the course of development of the Monophyidse, several ques- 

 tions are raised, some of which may serve as a directing clue 

 to a further investigation, while others can even now be an- 

 swered. In the first place, we have to find out whether (as 

 seems to me very probable) the other species of Monophyes 

 also present a third generation. In his ' Oceanic Hydrozoa/ 

 Huxley figures several species of Diphyes (pi. i. figs. 3, 4, 

 I). mitra and chamissonis) 7 in which a second nectocalyx was 

 not observed. These possibly represent Monophyids of the 

 structure of Muggicea. But it is not only for the Monophyidse, 

 but also for the whole of the Calycophoridce that, for reasons 

 which I shall indicate hereafter, proof of the occasional occur- 

 rence of a third generation may be obtained. A further 

 question, which we can even now answer in an affirmative 

 sense, is whether Monophyes primordialis, with its compli- 

 cated alternation of heteromorphous generations, really 

 represents the simplest Siphonophore, or whether it is not 

 rather to be regarded as a retrograde form. In deciding 

 against the latter conception, I depend not only upon its 



