448 M.T.Thorell on the Arrangement of the Copepoda. 
to the circumstance that what he calls mandibles I regard as 
maxilla, and his maxillz are, according to my view, the appen- 
dages of the maxille, maxillary palpi. The reasons on which I 
base my view are the following :—First and foremost, the organs 
in question are sometimes fused together, as in the genera Cory- 
ceus and Lichomolgus ; and it is more especially apparent in the 
last genus that the posterior ones are nothing more than appen- 
dages of the anterior ones, from the fact that they are not di- 
rected towards the opening of the mouth, but have their free 
border turned backwards. Now, since I know of no example in 
the Copepoda of the maxille taking the form of mandibular 
appendages, but several (among the parasitic forms) in which 
the palp separates itself from its union with mandible or maxilla, 
I have thought this sufficient reason for the supposition that the 
organs mentioned belong to the same pair. That I explain them 
as maxille,and consequently regard the mandibles as wanting, not 
the opposite, depends partly on the fact that they are situated 
further backwards than the mandibles of the Gnathostoma, partly 
and principally on the circumstance that I have found in two 
species of the genus Lichomolgus, precisely in the position occupied 
im the Siphonostoma by the proboscis with its enclosed man- 
dibles, a half-rostrum, which I conceive should be regarded 
as a rudimentary sucking-tube. Were Claus’s view correct, it 
would follow that ‘the mandibles” in the Copepoda in question 
must always want the mandibular palpi, and the “ maxilla” 
similarly always be without maxillary palpi. On the other hand, 
there is no lack of instances among the lower Crustacea of. the 
absence of the mandibles. Among the Ostracoda the mandible 
is represented in Cypridina by an appendage on the maxilla, and 
is altogether wanting in Philomedes. In the Copepoda I will 
only recall (to say nothing of the parasitic forms) the genera 
Sapphirinella, Claus, which for oral organs possesses only a 
pair of maxillary feet, and Monstril/a, Dana, which wants al/ the 
oral appendages. 
I have not been able to find, either among the forms known 
to me from autopsy or representations, any instance of actual 
transition between the oral organs of the Gnathostoma and 
Peecilostoma. Certainly, in the genera Candace, Dana, and 
Hemicalanus, Claus, the mandibles, in their longer and slenderer 
shape, and in offering only two teeth at the extremity, differ not 
a little from the usual form of the mandibles in the Gnathosto- 
mous series; and it is probable that they are used more as 
piercing- than as chewing-organs. But the presence of a strong 
two-branched maaillary palp, besides separate many-lobed maxille 
of the usual nature, shows at once that this genus cannot be 
referred to the Poecilostoma, but is essentially Gnathostomous. 
