448 M. T. Tiiorell on the Arrangement of the Copepoda. 



to the circumstance that what he calls mandibles I regard as 

 maxillae, and his maxillse are, according to my view, the appen- 

 dages of the maxillae, 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- 

 ccBus 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 maxillae taking the form of mandibular 

 appendages, but sevei'al (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 maxillce, 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 gennsLichomolgus, precisely in the position occupied 

 in 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 Clauses view correct, it 

 would follow that " the mandibles" in the Copepoda in question 

 must always want the mandibular palpi, and the '^maxillae" 

 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 Cyprndina 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 Monstrilla, Dana, which wants all 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 

 Poecilostoma. 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-hvanchedmaxillary palp, besides separate many-lobed maxillae 

 of the usual nature, shows at once that this genus cannot be 

 referred to the Poecilostoma, but is essentially Gnathostomous. 



