OF THE HOTATORIA. 459 



hand, I have obseiTed it in the young of Stephmwceros, Floscularia compla- 

 nata, and F. cornuta ; and Ehrenberg mentions it in F. ornata and Ladnu- 

 laria. In Stephanoceros, it was certainly associated with well-developed 

 jaws ; and hence I presume it is not exclusively an indication of the male 

 sex. The mass is sometimes broken up into fragments, of irregular size and 

 shape, and sometimes apparently pulverulent. In general, it appears to lie 

 loosely in the midst of the granular amorphous matter that occupies the pos- 

 terior region of the body-cavity ; but in Brachiomis Pala, and especially in 

 Br. amphiceros, I have fancied that I discerned traces of a vesicle, within 

 which the white substance seems to be contained. 



" On the nature of this substance I have no light from personal research. 

 Dr. Leydig, however, considers it to be a urinary concretion (Harnconcre- 

 mente), analogous to the chalky fluid which is d^charged by many insects 

 immediately after their evolution from pupae. 



" In the male oiAsplanchna BrightiueUn, there is, as its discoverer observes, 

 ^ a conspicuous round sperm-vessel, or testis, in which .... spermatozoa in 

 active vibratile motion may be seen.' Mr. DaLrymple, and subsequently 

 myself, also saw these, both mthin the sac and discharged by pressure. 

 Each spermatozoon, according to my own observation, consists of an oblong 

 body, yyi-^th of an inch long, and an abnipt, slender, \4bratile tail of equal 

 length. In the sperm-sac of A. Sieholdii, Dr. Leydig finds various seminal 

 elements, viz. round cells ; pyriform cells, drawn out to a fine point, and ad- 

 hering to each other by their rounded ends in a stellate manner ; oblong 

 bodies, with one side dilated into a free, undulating, membranous border ; 

 and slender, stiff", rod-like bodies, mth a central swelling; all containing 

 nucleated nuclei. On the male of A. priodonta, my observations were too 

 limited to determine more than the existence of the globular sperm-sac. 



" In Bmchionus ruhens and Br. MulJeri I found spermatozoa, which I have 

 above described. In the latter, the sperm-bag is of great size, and contains, 

 besides the spermatozoa of unusual development, slender spiculifonn bodies, 

 which may be the equivalents of the little rods described by Dr. Leydig in 

 Aspl. Sieholdii. The sperm-bag (in Br. MuJJeri) is closed posteriorly, as it 

 is also in Asj). Briglitwellii, by what appears to be a true sphincter ; and 

 such I conjecture to be the explanation of those diverging lines which 

 M. Dujardin saw in Enteroplea (so-called), which he considered to be pedi- 

 cles of his ' touffes de granules,^ while the ' tonffes ' themselves I take to 

 have been the masses of uiinary concrement. Dr. Leydig, however, con- 

 siders the whole to have been masses of spermatozoids. 



'' The outlet of the sperm-bag is, in all cases, by a thick protrusile and 

 retractile penis. Wherever a foot exists, this intromittent organ is continu- 

 ously united to its dorsal side, and is often so greatly developed that the foot 

 itself appears as an appendage. The protrusion of the organ, at least in most 

 of the examples that I have noticed, is by the eversion of the integuments. 

 WTien these are evolved to the utmost, the organ is seen to be a thick 

 column, conical or nearly cylindrical, with the extremity truncate, and sur- 

 rounded^ by a wreath of \ibratile cilia. It was doubtless the extremity of 

 the penis that M. Dujardin saw as ' un organe cilie entre Us muscles de la 

 queue,'' in the (so-caUed) Eiiterop>lea. The male of Sacculus viridis, a species 

 which is footless in both the sexes, is the only example in which I have not 

 seen the penis ; but the organ is probably wholly retractile within the body, 

 and my observations, on the only indi\'idual of this sex that I saw, were in- 

 sufficient to determine anything concerning it." 



That male Rotatoria have been recognized in comparatively few species, 

 admits of several explanations. The smaller size and comparative rarity of 



