382 



ENTOZOA. 



him that the four remaining equidistant, longitudinal vessels so 

 readily visible under low magnifying powers, are, in their turn, 

 referable to the so-called water-vascular system. 



Development. — The discovery of the viviparous mode of repro- 

 duction in Dracunculus is, I believe, due to Jacobson, yet it is only 

 within comparatively recent times that the importance of this dis- 

 covery has been fairly recognized. The structure of the young has 

 been ably investigated by Carter, Busk, Robin, Moquin-Tandon, 

 and others, and I had myself long ago detected certain anatomical 

 peculiarities respecting the precise nature of which we are stiU in 

 doubt. It remained for Bastian to clear up several of the missing 

 links in the chain of anatomical evidence, but by far the greater 

 number of the more needful facts in reference to the hfe-history of 

 our parasite are still concealed from view. Bastian, indeed, 

 advances a number of theoretical notions on this score, but I fear 

 they are little worthy of credit and, certainly, they are totally 

 opposed to what we know of the ordinary developmental processes 

 as they occur in nematodes generally ; in other respects, however, 

 his statements are both valuable and thoroughly trustworthy. 

 Bastian having carefully reviewed the writings of Busk, Owen, 

 Jacobson, and others, seems to have supposed that the greatly- 

 developed uterine organs had been altogether overlooked before 

 his time. For my part, I can only say that ten years ago I dis- 

 tinctly recognized these organs as nearly filling up the general 

 cavity of the body of Dracunculus, and, shortly after my investiga- 

 tions. Sir George Ballingall of Edinburgh, in the second edition of 

 his well-known work on " Military Surgery," expressly recorded the 

 fact in the following terms: — ^"The assistant-conservator of the 

 Anatomical Museum in our University has detected in the ovid/uct of 

 an adult specimen from my collection, myriads of minute and per- 

 fectly-developed (embryonic) Dracuncuh. They can be very well 

 seen with an half-inch object-glass, but their structure is best 

 exhibited if the magnifying power be increased to two hundred and 

 fifty diameters linear." These observations were, I believe, made 



