212 CTENOPHOR.E. Part II. 



radiated arrangement, the anterior and posterior sides can Ije fully ascertained. But 

 there u^ay Ije a compensation ibr this identity of the anterior and posterior sides 

 in the prominence of the lateral parts of the body. 



The parts already mentioned in a general way are not the only ones which 

 have refei'cnce to the bilateral arrangement. The tentacles also arise on opposite 

 sides, in two sacs extending inward in an obliquely vertical direction, and reaching 

 a point aljout as far from the actinal pole as the point from which the tentacles 

 issue is from the abactinal pole. These sacs stand in the interambulacral space 

 between the lateral rows of flappers, with their proximal surface near the fork of 

 the main trunks of the chymiferous tubes,^ which also branch in opjjosite directions 

 in the transverse diameter of the body. The disposition of this complicated system 

 is, therefore, also bilateral : two main trunks penetrating symmetrically right and 

 left from the funnel, and l)ranching in such a manner as to reach on each side, with 

 four arms, the four vertical rows of locomotive tlaj^i^ers, and giving on each side 

 also two l)ranches to the base of the tentacles.^ The chymiferous cavity is full 

 of fluid, which is in constant movement by the agency of vibratory cilia, and also 

 under the influence of a regular pulsation of the whole system in the two halves 

 of the body, so alternating in their contraction and dilatation, that at one time 

 the fluid moves to a considerable extent from one side to the other, and next 

 returns by the contraction of the opposite side through the same tubes in the 

 opposite direction, presenting something similar to what exists in Salpa under differ- 

 ent combinations. There is really a regular circulation through the large axial 



^ To facilitate comparisous witli the paper of Milne-Edwards is explicit upon that point. I am, 



Milne-Edwards on the gastro-vaseular apparatus of however, still inclined to question the absence of 



the Ctenophorte, I would remark, that he calls ven- cccliac tubes, which exist in all the Ctenophoi-aa I 



tricule chyliflre the axial chymiferous cavity, which have examined, and I have seen as many as seven 



I have QixWi^d funnel ; troncs pen'ffastrirjucs stipe- species of this order: the figures of Milne-Edwards 



rienrs, \\\vaI I have called iiiain trwils and forks of are drawn in a position in which the cicliac tubes 



the chyinil'i'ruus system ; vcu'sseaiix cos/aii.r, what I would be covered by the interambulacral tubes, and 



have called umbulacral tubes; vaisseaii periyas- might therefore be overlooked. Neither Eschscholtz 



trique vifeneur svperjiciel, what I have called inter- nor Mertens represents cccliac tubes in the species 



ambulacral or tentacular tube ; vaisseau periyas- of Cestuni which he has described. 

 trique infirieur profond, what I have called slom- " There are certainly two parallel interambu- 



achal or cceliac tithe. I would also take this oppor- lacral tulies to each tentacular appai-atus, as I have 



tunity to state, that the description of the chy- represented them in the Memoirs of the American 



miferous system of Cestum, published by IMilne- Academy, PI. III. Fig. 8 ; and Milne-Edwards must 



Edwards, has convinced me that this genus really be mistaken in representing only one. In a view 



constitutes a distinct sub-order, as I suspected ; for like that published by him only one tube is visible ; 



the course of the lateral ambulacral tubes is quite but, facing the trend of the tentacular sockets, both 



peculiar, and they are destitute of locomotive flappers. tubes are brought into sight. 



