12^^ ATr. II. J. Carter on the (hffonizntinn of Infusoria. 



the lower or iiiiicr part <if tho oriran, and at tliis jioint, thcroforp. 

 arc ))iish('(l inward as the vcsicula beconios distended (fitj;. 08 no). 

 Under the same circumstances, also, wlicn the vcsicula is slowly 

 dilating and contractinir, it may he seen to be attached to a small 

 papilla on the surface, about twice the diameter of those which 

 surmount the trichocysts*, and through which it probably 

 empties itself (fig. ()S a n). In Olosfninn there appears to be a 

 similar arranfrement of vessels round each vcsicula, and here also 

 they seemed t(» mc to be branched, — at least such was my im- 

 pression after having watched this animalcule for a long time, 

 in order to determine the ])oint. 



In Am(rba and Ac/inophri/s the vesieula is generally single ; 

 sometimes there are two, and nf)t unfrequently in larger Ammba a 

 greater number. In Encjlijplio 1 have not been able to recognize 

 them, but mArccUn vulgaris viWiXDiffluyia pr()t('iforinis{^\^^f^. 79,80) 

 they may be seen in great number, situated round the margin of 

 that part of the animalcule which is within the test; and from 

 their always reappearing, after contraction, in the same places 

 respectively, we may ])crha])3 infer that the situation of the 

 vcsicula in Ama'hn and Aciinoji/iri/s also is fixed, though from 

 their incessant jiolymoipliism it apjiears to be continually vary- 

 ing in position. In Parmnccium, and Khrenbcrg's Enterodela 

 generally, the vcsicula is cither singl(> or dual. When it exists 

 in great number in any of these {<?. g. Chilodun cucullulus, 

 Khr.), this a))pear8 to depend on accidental dilatations of the 

 sinuses in connexion with it. Thus, in the animalcule just 

 mentioned, where the vesieula is single, and seems to be sub- 

 terminal and lateral in its normal position, it is not unconnnon 

 to meet with a group in which every memlKr presents a variable 

 luimber of contracting vesicles, variably also and irregularly di- 

 spersed throughout the body, without one being in the true posi- 

 tion of the vcsicula (figs. 82, 83). That the vesieula does make 

 its ap])earance now and then may be inferred, as it perhaps may 

 alsft be inferred that from over-irritability, or some such cause, 

 it docs not remain under dilatation long enough to receive the 

 contcuts of the sinuses ; and hence their accidental dilatation, 



* These are narrow, fusiform cells, niTangcd perpendicularly, and at 

 •ome little distance from each other, under the pellicula, where they thus 

 form a layer all over the body, and each, accordinij to Dr. Alhnan, contains 

 a delicate, resilient thread, coiled up in its interior, which, just after the 

 cells have been forcil>ly pressed out into the water, by crushing the ani- 

 malcule, causes them to assume, for a second, a circular form, and then 

 burst, through which the thread is set free, and, lyinjr rigid on the glass, 

 presents the form of an acicidar crystal, terminated at each end by a 

 pointed extremity, one of which, being more attermated than the other, 

 appears like an ajipendage. To these cells Dr. Alhnan has given the name 

 of " trichocysts." (Quart. Joum. Microscop. Sc. vol. iii. p. 177, IH.05.) 



