320 GENERAL HISTORY OF THE INTUSORIA. 



and under other favourable circumstances, these sinuses run into continuous 

 hyaline lines, and may not only be seen extending in a radiated vascular 

 fonn across the animalcule, but even branching out roimd the position of the 

 vesicula, which, having now become permanently contracted, has thus poured 

 back the contents which render them visible. They enter the lower or inner 

 part of the organ, and at this point, therefore, are pushed inward as the vesi- 

 cula becomes distended. Under the same circumstances, also, when the vesi- 

 cula is slowly dilating and eontractiug, it may be seen to be attached to a 

 small papilla on the surface, about twice the diameter of those which sur- 

 mount the trichocysts, and through which it probably empties itself (XXYIII. 

 25). In Otostoma theie appears to be a similar arrangement of vesicles round 

 each vesicula ; and here also they seemed to me to be branched — at least 

 such was my impression after having watched this animalcule for a long time 

 in order to determine the point." 



" Of the use of the vesicula and its vascular system," Mr. Carter concludes, 

 <* we are at present ignorant, fiu'ther than that its fimctions are excretory ; 

 and when we observe the quantity of water that is taken into the sarcode 

 with the food, and try to account for its disappearance, it does not seem 

 improbable that the vesicula and its vessels should be chiefly concerned in 

 thi^ office. Another service, however, which it performs, is to bui'st the 

 spherical membranes of Vorticellce and Plcesconice when they want to retui^n 

 to active life after having become encysted : this it effects by repeated dis- 

 tension, until the lacerated cyst gives way sufficiently for the animalcule to 

 slip out." 



" Should it have any other uses, they are probably similar to those of the 

 ' water-vascular system ' of Rotifera.^" 



In answer to the question, if all vacuolar spaces, excepting those produced 

 by the deglutition of food, belong to this excretory system of contractile si- 

 nuses, he replies — " Certainly, where there is a pluraHtj^ of actively- con- 

 tracting vesicles without the appearance of the vesicula, as in Chilodon Cucul- 

 lulus, we may, as before stated, attribute this to a kind of over- irritability or 

 constrictive spasm of the vesicula, and therefore consider that these vesicles 

 are accidental dilatations of the sinuses in connexion with it, as we may set 

 down the dropsical state of Himantophorus Cfliaron (Ehr.), and other animal- 

 cules of the kind, to an opposite condition of this organ, viz. that in which it 

 is unable to reheve itself of its contents : this I have often seen occur under 

 my own eyes." 



Many thanks are due to Mr. Carter for his painstaking investigation on 

 this subject. We are nevertheless very doubtful of several of his details of 

 structure. For example, he describes globular sinuses to ajDpear around the 

 vesicle when an animalcule is exhausted, and those of Paramecium to run 

 into radiating hyaline (monihform) lines just before death and under a 

 certain amount of compression. Now, such conditions are ill-adapted to 

 accurate research ; and knowing how readily the integrity of the soft filmy 

 substance of the Protozoa is distm-bed, and diffluence induced, by unfavoiu^able 

 external circumstances, the observation in question must be received " cwn 

 grano salis.'^ Moreover, looking to most of his figui'es (which, we regret, 

 are rather diagrams than exact delineations after nature), the impression 

 forces itself upon the mind, that he has many times mistaken the commence- 

 ment of diffluence, and, in some instances, vacuolation resulting from the 

 entrance of water into the tissues, for the manifestation of sinuses about 

 the contractile vesicle or scattered over the body in connexion with it. 

 Thus we should rather attribute the several vesicles this naturalist saw in 

 different numbers, and variously and irregularly dispersed, in different spe- 



