608 DE. H. CHAELTON BASTIAlf ON THE ANATOMY AND PHYSIOLOGY 



motionless, spherical, or ovoidal bodies of a cellular nature, and as such they also exist 

 most frequently in the free species. Thus they are very small vesicular bodies in 

 Theristus acer (Plate XXVIII. fig. 22), larger in Comesoma vulgaris (Plate XXVIII. 

 fig. 23), much larger ovoid bodies of the same kind in Monhystera ambigua, ^-J-y" in 

 diameter (Plate XXVIII. fig. 24), and small pyriform corpuscles in Enoplus comrmmis 

 (Plate XXVIII. fig. 25). 



In Rhabditis marina I have seen the spermatozoa presenting totally different charac- 

 ters; they appeared as short cylindrical bodies Tinro" ^^^?i (Plate XXVIII. fig. 13), 

 having moreover a slowly oscillating movement, which was seen to continue for more 

 than twenty-four hours. In Monhystera di»juncta the spermatozoa were linear bodies 

 TolTs" ill length (Plate XXVIII. fig. 26), having a slowly serpentine movement. The 

 spermatozoa of Dorylaimus stagnalis are most frequently met with as bright highly 

 refractive bodies, enclosed within a hyaline vesicle, though a later stage of evolution 

 seems to convert them into free filamentous bodies x^cjtj" long, and narrower at the 

 extremities than in the middle (Plate XXVIII. figs. 8 & 9). It seems probable that 

 the spermatozoa of different species are not always in the same stage of development 

 when emitted from the male; in some cases they appear to continue their development 

 within the female organs of generation, before coming into contact with the ova. 



The only Nematoids I have seen in actu coitus were specimens oi. Cephalohus persegnis ; 

 the male was coiled around, at right angles to the female, in the same fashion as was 

 observed by Duges with specimens of Anguillula acefi, and as others have noticed in 

 certain of the parasitic species. 



There seems to be no fixed period of the year which may more especially be considered 

 as the breeding-season of these animals; in spring, summer, autumn, and mid-winter 

 alike I have found amongst the free species females containing impregnated ova. In 

 the majority of these animals, too, the ova are very large in proportion to the size of 

 the body, and few in number — in both respects presenting a striking contrast to what is 

 usually met with amongst the parasitic forms. The two divisions of this order agree, 

 however, in the fact that, whilst the majority of the species are oviparous, the remainder 

 are viviparous, bringing forth active young, presenting in a miniatui'e form the external 

 characters of the adult animals. 



DEVELOPMEI^T. 



Under this head I have nothing new to say concerning the early development of the 

 ovarian cells and spermatozoa, or the actual process of fecundation in the Nematoids. 

 This has been treated of most fully with reference to the parasitic species by Nelsox, 

 BiscHOFF, Leuckart, Meissnee, and Allen Thompson, and as it occurs amongst the free 

 Nematoids by Davaine and Cartee ; and for the results of their investigations I must 

 refer to the various periodicals in which these observations were recorded. To have 

 gone over this ground, and to have endeavoured to reconcile discrepancies at present 

 existing in the accounts given by these various anatomists, would of itself have been an 



