284 Mr A. J. Carter on the Organization of Infusoria. 



water, and then disappears, while, the vesicula dilating again, 

 the r ,ame phenomena may be repeated sufficiently often for the 

 observer to feel certain that the fluid which accumulates in the 

 vei ila is uncoloured and that it is ejected externally. 



If, then, the water with which the vesicula is refilled comes 

 from the exterior, as Cohn's experiment goes to prove, those 

 who support this view will be inclined to state that, as it passes 

 into the vesicula of Brachionus urceolaris, it is strained clear, 

 and as it passes into that of B. militaris it is not so. But the 

 sudden way in which it is ejected in B. urceolaris indicates a 

 very large opening, and one which would admit the finest colour- 

 ing matter that can be used, and which was used on the occasion 

 of the experiment above-mentioned, viz. fine China-ink (or, as 

 it is termed, " Indian ink "), very easily. Similar results were 

 obtained by using carmine with a large Notommata. 



The assumption that it is strained in one instance and not in 

 the other, then, is not sufficient to lead to the conclusion that 

 the vesicula is filled from without ; and therefore, disregarding 

 Cohn's statement, I still assert that the fluid is gathered from 

 the interior, conducted into, and expelled by, the vesicula. 



Thus we have further confirmation of the vesicula being an 

 excretory organ in the Infusoria, as well as the fact of its being 

 so not only in Brachionus, but probably in the Rotatoria gene- 

 rally, so far established. 



Besides the monociliated tassel-like bodies which are attached 

 to the vessels of this system in the Rotatoria, the vessels are 

 accompanied by a fine granular substance, which more or less 

 envelopes them ; and this is particularly well seen in the seg- 

 ments of the Naidina (worms), where there is an organ of this 

 kind in each segment, called by Dr. T. Williams the " segmental 

 organ." (See my description of this, and figure, Ann. Nat. Hist, 

 vol. ii. p. 27, pi. 2, 1858.) 



It is not my intention to allude further to this granular sub- 

 stance now ; but, as regards the ' tassel-like ' bodies, I cannot 

 help observing that they are as much indicative of the excretory 

 nature of this system as any other part. Witness them in one 

 of the largest species of Rotatoria, viz. in Notommata, where 

 they exist in scores on one long vessel on each side, while the 

 other long canals have none at all, but are surrounded by the 

 granular matter. Here some of the tassel-like bodies are pro- 

 vided with the usual single cilium running through them, while 

 others are destitute of it, but have in lieu expanded mouths 

 fringed with cilia. Does not the cilium act after the manner of 

 a "spiral pump " in raising the water from the abdominal cavity 

 into the tubes, and has not the ciliated border the same effect 

 as the single cilium of Euglena, &c., and the fringe of cilia round 



