8 THE VOYAGE OF H.M.S. CHALLENGER. 



tliat from wliicli the designation Scbizopoda has been dei-lved. There are, it is true, 

 some few examples of Macruraus in lilce manner retaining the exopods tliroughout the 

 adult stao-e, viz., the anomalous families Ephyridse and Pasiphaida3, as also certain of 

 the Penseidea ; but in none of those forms do these parts exhibit the strong develop- 

 ment peculiar to the Schizopoda, nor do they seem to have any importance as organs of 

 locomotion. 



2. As to tlie oral parts, may be noticed the large size of the mandiljular palp, which 

 generally even exceeds in length the body of the mandible itself. The maxillse, too, 

 also exhibit a rather peculiar appearance, different from what is observed in any true 

 Macruran. It may, however, be remarked, that the oral parts in the Eupliausiidse differ 

 in several respects very materially from those in other Schizoj^oda. 



3. Of the legs, as a rule, only the foremost pair are developed as true gnathopoda, 

 whereas all the others generally exhibit a very uniform structure, nt)ne of them Ijeing, as 

 is the case in other Podoplithalmia, modified to cheliform or prehensile organs. In the 

 Euphausiidae, too, not only are all the legs as a rule uniform, Ijut even the maxillipeds 

 are quite pediform in structure. The genus Euco'pia exhibits, it is true, in this respect 

 a very striking anomaly ; it appears, however, that the very peculiar structure of the 

 legs in that genus is quite as different from what is typical in the higher Podophthalmia. 



4. The nK^de in which the ova are borne in the females differs essentially from what 

 has been ol)served in any other known form of Podophthalmia. In those Crustacea, as 

 is well known, the caudal limbs (pleof)oda) serve for affixing the roe, whereas in the 

 Schizopoda the ova are invariably placed beneath the trunk, generally enclosed within -a 

 pouch, or marsupium, consisting, as in Amphipods and Isopods, of a certain number of 

 lameUiform leaflets, issuing from the bases of the legs. True, in the Eupliausiidse, 

 incubatory lamellae are wanting ; but even here the position of the o^-a Iteneath the 

 trunk is precisely the same as in other Schizopoda. 



5. The development of most Schizopoda exhibits a very striking resemblance to that 

 of the Isopoda, the young passing within the marsupium of the female through one 

 or more so-called pupa-stages before being hatched. In the Euphausiidae, however, a 

 totally different mode of development has been discovered, the young of these animals 

 being hatched in a very immature condition, and not attaining, till after an exceedingly 

 complicated free metamorphosis, the form characteristic of the adults. 



The Schizopoda occupy, as it were, the most primitive jjosition within the division of 

 the Podophthalmia, being apparently the least modified forms, in which the original 

 characters distinguishing the progenitors of the whole division would seem to exhiljit 

 least change. This view derives, too, undeniable confirmation from the fact that a vast 

 number of the higher Podophthalmia (Macrura, Caridea) pass during development through 

 a larval stage — the so-called Mysis-stage — calling to mind in a most striking manner the 

 Schizojiod tvpe. 



