LrBBOCK OX SPH^EULAEIA BOMBI. 47 



celebrated chapter on the snakes in Iceland, and say simply that there 

 are in Sphaerularia, no muscles, no nervous or circulatory systems, and 

 no intestinal canal. 



A priori it would seem almost impossible that an animal could 

 exist without these organs. Muscles, however, would be useless, or 

 even destructive. So long as the Sphaerularia remains quiet, the Bee 

 does not seem incommoded by its presence, which perhaps produces 

 scarcely any abnormal sensations ; but if the parasite, being so large in 

 proportion to its victim, were to move about, it would probably so affect 

 and disarrange the viscera of the Bee, that the poor insect would be 

 quite unable to pursue its usual avocations, and would quickly perish. 

 The female Sphaerularia being thus, when full-grown, reduced to a 

 merely vegetative existence, the nerves of motion and of sensation must, 

 of course, be useless, and would soon become atrophied. Under these 

 circumstances, however, it might have been expected that the digestive 

 organs and their nerves would have been highly developed. That, 

 on the contrary, these organs are also absent, is probably to be ex- 

 plained by the fact that the animal is bathed on all sides by the blood 

 of the bee, and thus lives in a medium which is highly organized, and 

 requires, probably, scarcely any further elaboration. 



Moreover, although this absence of certain important parts is carried 

 to an extreme in the present animal, we find in other JSTematoids a con- 

 siderable approach to the same condition. Iudeed, until within the last 

 few years, we had scarcely any reliable knowledge of the nervous sys- 

 tem in any of the ]S"ematoids ; lately, however, it has been figured and 

 described at length in several genera, as, for instance, in Strongylus, 

 Ascaris, Oxyuris, Gordius, and Mermis; but even in Yan Beneden's 

 Prize Memoir, " Sur les Vers Intestinaux," the nervous system is 

 scarcely so much as mentioned ; and it seems very doubtful whether the 

 filaments referred to by Meissner in Mermis as nerves, do not rather be- 

 long to the muscular system; while the so-called supra-oesophageal gan- 

 glion is asserted by Schneider to be really the oesophagus. 



In the JNematoids generally the intestinal canal is a straight tube, 

 reaching from one end of the body to the other. In Mermis and Gor- 

 dius,* however, we meet with a totally different and very abnormal 

 type, which it is unnecessary for me here to describe. It is sufficient to 

 say that, whereas in these two genera there is no stomach, and that, 

 while in Mermis the oesophagus is small, and in Gordius quite rudi- 

 mentary, I have in the mature female Sphaerularia been unable to de- 

 tect any trace of them at all. 



The same is the case with the muscular system. I have often 

 opened the body along one side, and then stretched out the skin. In 

 this manner it may be examined with a high power; but I have never 

 been able to see any structure in the least like muscular filaments. The 

 entire absence of motion confirms this view. 



* The intestinal canal is quite short also in some other worms, as, for instance, in 

 Nemertes. 



