8 THE VOYAGE OF H.M.S. (JHALLENGER. 



that from which the desiguatiou Schizupoda has Ijcen derived. There are, it is true, 

 some few examples of i\Iacrurans in like mauner retaining the exopods throughout the 

 adult stage, viz., the anomalous families Ephyridse and Pasiphaidse, 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 the oral parts, may be noticed the large size of the mandibular palp, whicli 

 generally even exceeds in length the l_)ody of tlie mandible itself. The maxilla, too, 

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

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

 in several respects very materially from those in other Schizopoda. 



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

 whereas all the others generally exhiljit a very uniform structure, none of them being, as 

 is the case in other Podophthalmia, modified to eheliform or prehensile organs. In tln' 

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

 are quite pediform in structure. The genus Eucopia 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 diff"erent from what is typical in the higher Podophthalmia. 



4. The mode in which the ova are borne in the females differsr cssentiallv from what 

 has been observed in any other known form of Podophthalmia. In those Crustacea, as 

 is well known, the caudal limbs (pleopoda) 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 Amphii)ods and Isopods, of a certain number of 

 lamelliform leaflets, issuing from the liases of the legs. True, in the Euphausiida", 

 incubatory lamellai are wanting; but even here the position nf the ova lieneath 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 lias l)een 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 position 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 exhibit 

 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 

 Schizopod type. 



