338 Miscellaneous. 



of the host, and it is extremely difficult to extricate it entire ; a cyst 

 protects the parasite throughout the whole of its length. 



Gymnorhyncliiis reptans M'as hitherto unknown in the perfect 

 state : I have had the good fortune to meet with it in this state in 

 Oxi/7-hina r/lauca. Jhvon de Guerne found at Concarneau in the 

 intestine of this shark some worms of large size, which he was good 

 enough to hand over to me to study ; they unquestionably belong 

 to this species. 



The individuals observed reach the length of 30 centim., while 

 the breadth of the neck scarcely exceeds that of the initial portion 

 of the chain ; but this organ is much thicker, since it attains a 

 depth of 2 millim., while the first segments only measure about 

 half a millimetre ; the ripe segments are almost square, measuring 

 4-5 to 5 millim. in breadth by 5 to 6 millim. in length ; they are 

 swollen in the middle and marked at this point with a broad brown 

 epot, which corresponds to the mass of ova ; the other segments 

 diminish successively in size until we come to the head. 



Contrary to what was supposed by van Bcneden, the vesicle into 

 which the anterior portion of the larva retracts itself, as well as its 

 enormous appendage, do not pass over to the final animal and do 

 not become sexual ; they are digested by the new host, and of this 

 exceedingly long animal there remains absolutely nothing but the 

 neck and that diminutive portion of the tissues which prolongs it, 

 and which we formerly called the generative zone, at the expense of 

 which the chain of segments is ibrraed. 



We may ask ourselves what is the morphological significance of 

 the appendage which prolongs the vesicle of Gt/mnorhi/nchus in the 

 larval state — an appendage which is not found or which is very 

 rudimentary in the forms allied to this species : there is no doubt 

 that this is a structure perfectly comparable to that which we have 

 pointed out in several Cestodes of the type of Tcpma scrrcda, wliich 

 exists in many other Ccstode larva?, if not in all, and which we 

 notice in particular in all those Cysticerci recently found in fresh- 

 water Crustacea. This portion of the body, which corresponds to 

 the hexacanth embryo, develops but little, or frequently falls otf at 

 an early period, remaining simply indicated at the extremity of the 

 Cysticcrcus by an umbilicus of which we have explained the mode of 

 formatiim. It is necessary to note that, in the particular case of Gtim- 

 norhynchus, the appe!>dage is not degenerating, and that it retains 

 a large degree of vascularity and does not show' any laceration in 

 the centre ; it is a mistake, moreover, to have represented it as 

 jointed, since it only presents simple folds in its entire length. 



I would add, in conclusion, that the dimensions of Gymnorhyn- 

 ehtts in the perfect state prevent the conclusion, advanced by Orley 

 in a positive manner, that the Cestodes of the cartilaginous fishes are 

 always of small size. — Comphs liendus, tome cxiii. no. '2-i (^December 

 U, 181)1), pp. 870, 871. 



