REPORT ON THE SCHIZOPODA. 221 



Kroyer, thougli unquestionably distinct from the Arctic form Dajus raysidis, Kroyer. 

 The adult female (figs. 12, 13) has, in its external apijcarancc, a very striking similarity 

 to certain jDarasitic Copepoda, the anterior division of the body being greatly expanded 

 and of a rounded triangular form, with a sHghtly indicated segmentation, whereas the 

 posterior part, or tail, is abruptly narrowed, more distinctly segmented, and terminates 

 in two simple lamelliform appendages, reminding one of the so-called furca of the 

 Copepoda. The five pairs of clasping legs are (see fig. 13) crowded together on either 

 side of the buccal area, which occupies about the centre of the ventral face of the anterior 

 division. The male (figs. 12, 13, a, 14) difi'crs, as in the typical species, materially from 

 the males of the preceding forms, in having the tail distinctly segmented and furnished 

 with well-developed pleopoda, as also with a pair of biramous uropoda. It is found with 

 its anterior part deeply immersed in a hollow space of the female, lying ventrally at 

 the end of the anterior division, and partly defined by two wing-like, posteriorly pointing 

 cuticular folds (see fig. 13), the remaining part of its body projecting freely behind in the 

 same axis as that of the female. Both the female and the male, but more especially 

 the latter, are variegated with dark pigment deposits over their dorsal face. This 

 peculiar form was found attached to the ventral fiice of the trunk posteriorly on a few 

 specimens of Siriella thompsoni (Milne-Edwards), both males and females, in the latter 

 lying 'partly within the marsupial pouch, as was also the case with Dajus mysidis. It 

 may justly be named Dajus siriellce, n. sp. 



Endo-Parasites (PI. XXXVIIl. figs. 1 5-23). 



The two forms of parasites treated on under this head were both found within the 

 body cavity of certain Euphausiidaj, their bodies freely suspended in the peri^•isceral 

 fluid of the Schizopods, and not covered by any particular envelope or cyst. They 

 evidently belong to two diff'erent groups of intestinal worms, the one l)eing an Acantho- 

 cephalan, the other a Trematode. Concerning both, I have thought it right to consult 

 the celebrated German Professor Rudolf Leuckart, unquestionably the greatest authority 

 as regards intestinal worms, and he has most cordially given me his suggestions respecting 

 the present interesting forms. None of them can, according to Professor Leuckart, be 

 reo-arded as sexually mature, but represent a mere transitory stage, that probably does 

 not arrive at full maturity, before being transferred into the intestinal canal of some 

 higher animals, most likely fishes or whales, which arc both known to feed largely upon 

 Euphausiida3. In their present stage of development they simply absorb through the 

 skin the perivisceral fluid, in which their bodies are suspended, and are thus placed under 

 particularly favourable conditions of life, whence their comparatively large size, in pro- 

 portion to the size of the Schizopods infested by them. 



The form represented in figs. 15-18 is readily recognised as a species of the genus 



