396 



ROTIFERA. 



spines, and is, moreover, provided on each 

 side with a broad plate of horn, adherent to 

 the glans by its inner border, while all its 

 outer free edge is armed with strong sharp 

 teeth resembling those of a saw (fig. 285.) ; a 

 structure which is additionally remarkable 

 from the circumstance, that in the females 

 of the species thus barbarously armed, the 

 vagina offers no peculiarity in its appearance. 



In connection with the male organ of 

 generation may be noticed the preputial 

 glands, which, 'in some of the Rodentia, are 

 very largely developed. This is more espe- 

 cially the case with the beaver, in which 

 animal they secrete the drug castoreum, once 

 much used in medicine. These glands form 



Fig. 28G. 



remarkable on account of the prominence and 

 number of the ova which they contain, giving 



Fig. 287. 



Preputial glands of the Beaver. 



a, the prepuce laid open ; c, attachment of the 

 prepuce around the neck of the penis ; d, body of 

 penis ; c, e, opening of the inferior preputial glands ; 

 f, i, in, stylets passed into the ducts of these glands ; 

 h, I, o, the glands which on the right side are laid 

 open, to show their internal structure ; p, superior 

 large glandular sac ; r, ditto of the opposite side, 

 laid open to show its interior ; q, opening of these 

 sacs into the preputial canal. 



several wide pouches (Jig. 284-. e,f, g,h, i, k), 

 situated on each side of the perputial sheath. 

 The structure of these glands is shown in 

 fig. 28G. ; they are arranged in two sets, of 

 which the lower, three in number on each side 

 (k, /,o), are found when opened, as represented 

 on the right hand side of the figure, to be 

 hollow, the walls enclosing their central cavity 

 being made up of numerous small glandular 

 masses, that secrete a thick yellowish fluid. 

 The upper set consists of two capacious 

 ba^s (p), which, when opened, are seen to have 

 their lining membrane (V) deeply rugose. ' The 

 secretion of these pouches is of a deep grey 

 colour, and, if possible, more disagreeable. 



Female organs of generation. The ovaria 

 in the female Rodents occupy the same posi- 

 tion us in other Mammifera, and are chiefly 



Generative organs nf the female flare. 



a, vulva ; b, vagina ; c, orifice of the urethra ; d, 

 urethra ; e, f, cornua uteri ; g, termination of the 

 cornua uteri by two separate orifices (ora itteri\ 

 into which the probes, h, i, have been introduced ; 

 k, I, the ovaria ; n, o, Fallopian tubes ; p, the anus ; 

 q, anal gland ; r, cavity situated between the 

 vulva, a, and the rectum, s. 



them a somewhat racemose appearance. The 

 uterus is always deeply divided into two long 

 cornua, and this division is in some cases 

 carried to such an extent that the body of the 

 uterus constitutes but a very insignificant 

 part of this viscus, and is even absolutely 

 wanting, as, for example, in the hare and in 

 the rabbit, in which animals the cornua uteri 

 open separately into the upper part of the 

 vagina, so that the uterus is literally here 

 double, as represented in the appended 

 figure (Jig. 287.), where two probes (h, i) are 

 introduced into the two distinct openings, 

 whereby the two cornua uteri communicate 

 with the vagina. 



The vagina presents no peculiarity of struc- 

 ture, even in the females of those genera in 

 which the penis of the male is furnished with 

 the remarkable armature described above. 



The mammary glands in the Rodentia vary 

 much in number, some, as the agouti, having 

 as many as from twelve to fourteen nipples ; 

 whilst in others, such as the Guinea-pig, there 

 are but four. 



(T. Rymer Jones.) 



ROTIFERA, or ROTATORIA, the name 

 of a class of invertebrate animals which are 

 characterised by the absence of a medullary 

 chord and pulsating vessels; by the possession 

 of a simple tubular alimentary canal ; a defi- 

 nite form ; a reproduction neither fissiparous 

 nor gemmiparous ; the reproductive organs 

 of both sexes in the same individual. 

 Their movements are effected by peculiar 

 rotating organs, and they have no true ar- 

 ticulated feet, but mostly a single false foot. 

 The creatures thus constituted are often called 

 wheel-animalcules, from the wheel-like motion 



