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. 
Gymnorhynchus reptans was hitherto unknown in the perfect 
state: I have had the good fortune to meet with it in this state in 
Oxyrhina glauca. Baron 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 
spot, 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 Beneden, 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 enimel 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 formed, 
We may ask ourselves what is the morphological significance of 
the appendage which prolongs the vesicle of Gymnorhynchus 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 Tenia serrata, which 
exists in many other Cestode larvae, 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 off at 
an early period, remaining simply indicated at the extremity of the 
Cysticercus by an umbilicus of which we have explained the mode of 
formation. It is necessary to note that, in the particular case of Gym- 
norhynchus, the appendage 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- 
chus 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.-—Comptes Rendus, tome exiii. no. 24 (December 
14, 1891), pp. 870, 871. 
