608 DE, H. CHARLTON BASTIAN ON THE ANATOMY AND PHYSIOLOGY 



regards the free Nematoids that they undergo their development at once in the regions 

 where they are bom, in association with their parents, and other kindred species, young 

 and old : generation succeeding generation in the same external habitat, and parasitism 

 neither entering into nor being required by them in any stage of their simple life-history. 

 In these therefore the whole process of development might be studied, provided the 

 young animals could be kept alive and under observation during the period necessary for 

 this investigation. I have not had much time to devote to this portion of the subject, 

 and consequently have only a few rather unconnected details to bring fonvard, partly 

 concerning the parasitic and partly concerning the free species. 



In a former paper on the Guineaworm* I alluded to the various accounts that had been 

 given concerning the anus and the termination of the intestine in the young contained 

 within this animal. Amongst others I mentioned the description which Carter had 

 given of the intestine terminating " at the root of the tail," near what I have described as 

 lateral saccules and he as a gland. I had seen another disposition of the intestine so 

 plainly that I was inclined to believe Carter must have been mistaken ; and it did not 

 occur to me that the discrepancy in our observations might be fully accounted for 

 by the fact of our having examined young animals at different stages of their deve- 

 lopment. Now, however, I feel assured that this is the most probable explanation of 

 the former discordance in our views, since in three or four Guineaworms of different 

 sizes which I have since examined, I have found a difference in the degree of develop- 

 ment presented by their contained young ; and in one animal I found them in a more 

 advanced stage than I had ever before seen, displaying the intestine communicating 

 with the exterior by an anal orifice in the very situation indicated by Carter — that is 

 to say, slightly above the level of the lateral sacculi (Plate XXVII. fig. 22, a). Thus the 

 young which I had before examined and figured, in which the intestine ended caecally, 

 were less mature individuals, and so exemplified what appears to be the usual course in 

 the development of the intestinal canal in higher members of the animal kingdom. It 

 exists first in the form of a csecal tube which gradually elongates, so as to approximate 

 and ultimately unite with an anal orifice commencing independently as an infolding of 

 the parietes of the body. That the young I first examined were less mature is also 

 indicated by the fact that the measurements I gave of them were below those given of the 

 young Bracunculi by several other observers. In these last more developed animals in 

 which I have been enabled to detect the anal orifice, I also recognized rudimentarj- con- 

 ditions of the two head papillae, and, more interesting still, discovered what has not yet 

 been detected in the adult animal, in the form of a distinct channel through the integument 

 in. the ventral region of the body, about 3^" from its anterior extremity (Plate XXVII. 

 fig. 24, a). May not this be the commencement of one of the forms of the ventral ex- 

 cretory apparatus met with in the Nematoids 1 Whether, however, it is the outlet of a 

 future rudimentary saccule, or of two longitudinal vessels which are to exist in the lateral 

 regions of the body, cannot be said. In the adult Dracunculus I have now recognized 



* Trans, of Linn. Soc. vol. xxiv. p. 122. . 



