456 GENERAL HISTOJir OF THE INEUSORIA. 



short tube, which, as a rule, lies free upon the foot, and extends nearly to its 

 extremity. Its inner canal, and its external border, exhibit vibratile action. 

 The foot is transversely wrinkled, and ends in two small toes. About the 

 origin of the penis from the testicle are two club-shaped glands which pour 

 their secretion into the canal ; and near them is the contractile vesicle, giving 

 off its resj^iratory canal on each side, with the usual tag-like appendages. 

 Several spherical cell-looking bodies occur about the head, with the largest 

 of which the eye-specks are in connexion, and w^hich may therefore be con- 

 sidered the cerebral ganglion. Upon the testis, near its lower end, two or 

 three vesicles are placed, filled ^\^th dark granules, resembling those seen in 

 EnteroiDlea Hydatina, and of which we cannot predicate further than that 

 they are not of the natui^e of m^inary concretions (as Leydig imagined), but 

 in some way belong to the sexual apparatus, or else are unconsumed cells 

 of the yelk-mass. 



The tubular or band-like prolongation from the upper extremity of the 

 testicle, noticed by Cohn, and considered by him a '' suspensor testis," repre- 

 sents, in Leydig's opinion, rather the nidiment of the undeveloped alimentary 

 tube. This author likewise denies Cohn's statement that the walls of the 

 testis are thick and muscular, asserting that they consist of a thin membrane. 



The spermatozoa, i. e. the fecundating male particles, have been described 

 by Mr. Dahymple, Gosse, and Leydig. We borrow the description of the 

 latter as the more recent : — " The testicle (XXXYII. 29 c) of Notommata 

 Sieboldii is at once seen to be more or less completely filled with spermatozoa, 

 arranged about the excretory duct in a radiating manner; when not too much 

 compressed, they move about within the testis. On isolating by slight pres- 

 sure the contents of the organ, may be noticed, 1, large round vesicles, in 

 which, by a stronger magnifying power, two, or probably more, hyaline nuclei 

 with nucleoli, entii'ely occupying the space, may be distinguished (XXXYII. 

 30 e) ; 2, somewhat larger cell-formed elements, disposed in a radiating 

 manner about a centre, and larger towards one side (XXXVII. 30 c) — at 

 the rounded extremity a clear nucleus, with a nuclear coi'puscle, is always 

 placed ; 3, elongated, mostly falcate or curved structures, which have the 

 before -mentioned nuclei in their interior, and on one margin are expanded 

 into an evidently undulating membrane (XXXYII. 30 a, b, d). They move 

 about, and swim hither and thither, in such a manner that they remind one 

 not a little of many Infusoria, having a clear sharply- defined contoiu- and a 

 rod- like figure, mth a sHght enlargement at the middle. It is these bodies 

 which lie around the commencement of the excretory duct, and give rise to 

 the apparent striation above aUuded to." In Hydatina senta the spermatozoa 

 are likewise of two forms, and are noticed sometimes to have a swarming 

 movement even within the testis. 



Leydig has been imable to satisfy himself whether the stave- or rod-like 

 variety (XXXYII. 30/) is to be considered the ripest of the spermatozoa, 

 and derived from one of the other forms, or whether there are two sorts of 

 spermatozoa in Notommata Sieboldii, as there are in Paludina vivijpara, one 

 of the MoUusca. 



Perty states briefly and generally, of the spermatozoa of Eotatoria, that they 

 have a broad-oval refracting body, and a tail-like appendage. 



The spermatozoa have been seen within the abdominal cavity of not a few 

 female Rotifera, freely moving about wdthin it. For instance, it has been 

 witnessed in Braehio7ius, Conocliilus, Lacimdaria, Megalotrocha, and Hyda- 

 tina. It is not known how they reach this cavity, since the cloaca into 

 which they are normally received is a closed sac. Cohn imagines they may 

 enter through some aperture in the integument as yet unnoticed ; it is, how- 



