158 Dr. C. Chun on the Siphonophora. 



it is placed at the bottom of a pit-like depression. But if we 

 observe the perfectly mature ova, we find that the nucleus 

 gradually arches up and the depression disappears, until 

 finally the nucleus, enveloped by the adjacent plasma, projects 

 above the periphery of the ovum as a lenticular elevation. 

 The delicate ectodermal envelope is at the same time also a 

 little pushed forward and stretched. In a short time the con- 

 vexity disappears rapidly, and the nucleus draws back again 

 so far that a pit-like depression is again produced. In this 

 way, then, pumping movements are executed at one part of 

 the surface of the ovum pretty regularly, about twice in a 

 minute, their purpose evidently being to burst the thin ecto- 

 dermal envelope and to render possible the exit and fertiliza- 

 tion of tjie ovum. As a matter of fact, indeed, we find that the 

 ova are evacuated from the manubrium singly, and not simul- 

 taneously. 



To judge from our previous knowledge of the development 

 of the Siphonophora, we should expect that from the fertilized 

 egg of Eudoxia Eschscholtzii the Muggicea would originate. 

 I was therefore not a little surprised when, in my pelagic 

 captures, I met with an elegant Siphonophore which at the 

 first glance showed itself to be a true Monophyes, and yet 

 presented stomachal sacs and urticating batteries which, even 

 by the most careful examination, were not to be distinguished 

 from those of Eudoxia Eschscholtzii \ As regards the organi- 

 zation of this smallest and most simply constructed colony 

 among all the Siphonophora, which has been seen by no 

 previous observer, it consists essentially of a medusiform 

 nectocalyx, a stomachal polyp, and a tentacle (fig. 1) . The 

 calyx is cap-shaped and of laterally symmetrical form. The 

 dome of the umbrella appears drawn out into a lappet and 

 rounded off. Close to the place of insertion of the other 

 appendages two gelatinous pads arise as the first indication of 

 an incomplete sheath. Four vessels, originating from the 

 base of the fluid-receptacle, which traverses the umbrella ob- 

 liquely and is furnished with an oil-drop, supply the subum- 

 brella, finally opening into an annular canal placed upon the 

 velum. I have already indicated that the stomachal sac and 

 the tentacle exactly agree with those of Eudoxia Eschscholtzii. 

 Only the youngest examples, however, are so simply con- 

 structed as the Monophyes just described ; a further compli- 

 cation may be observed in somewhat older specimens. Thus 

 the stomachal sac and the tentacle are somewhat removed 

 from the base of the fluid-receptacle, and communicate with 

 the latter by means of a contractile portion, the first indication 

 of the stem. On the other hand new rudiments of buds make 







