REPORT ON THE CIRRIPEDIA. 1<I 



diverges in many respects from the typical structure of Cirripeds ; yet, though perhaps a 

 certain resemblance with some of the parasitic Isopoda is not to be denied, it would be 

 hazardous, contrary to the authority of de Lacaze-Duthiers, to doubt its Cirripedial 

 nature. The points in which it differs from the true Cirripedia are the following : — 



1. The shell (carapace, test) has a very remarkable form, which perhaps slightly 

 resembles that of the true parasitic Cirripedia (Sacculina, &c). It almost entirely 

 envelops the body, leaving only a very small aperture, and consists of a cartilaginous 

 outer and a soft inner layer. Between the two layers the female genital organs and 

 the liver are situated. 



2. The extremities are one-branched, and bear a very remarkable relation to the 

 genital organs ; the oviducts open at the base of the first pair ; the testes are placed in 

 the four following pairs of limbs, and open at the basal joint of each leg with a distinct 

 aperture. The sixth pair is short, and has nothing to do with the genital organs. 



3. The structure of the head, with its small antennae, and the parts of the mouth 

 united to compose the " calotte cephalique." The latter forms a suctorial apparatus, 

 which, however, according to Lacaze-Duthiers, is rudimentary in the adult animal. 



4. The absence of the organs of respiration, and the high development of the 

 circulatory apparatus. 



5. Also the way in which the adult animal takes its food ; the shell is overgrown by 

 a polype (Gerardia), and the Laura sucks its food by means of ramifications of the 

 capillaries which are spread through the shell, and which penetrate with countless roots 

 the tissue of the polype. 



6. Finally, the structure of the abdomen, which is distinctly segmented, the hinder- 

 most segment terminating in two anal appendices (pieces anales). 



Lacaze-Duthiers proposes for this curious parasitic Crustacean a distinct group in the 

 sub-order of the abnormal Cirripedia, which he calls the Ascothoracida or Rhizothoracida. 

 No doubt the mutual relations of these abnormal Cirripedia with each other, as well as 

 with the Cirripedia Thoracica, are still very imperfectly known, and new investigations 

 are necessary. 



NOTE ON THE RHIZOCEPHALA. 



The naturalists of the Expedition have recorded the occurrence of Pdtogaster in their Station Books and 

 Journals several times during the cruise, viz. : — Station 158, March 7, 1874; lat. 50° 1' S., long. 123° 4' E.; 1800 

 fathoms ; south of Australia, one specimen in the pouch of Hymenaster. On this specimen R. v. Willemoes 

 Suhm has the following note : — " In the cavity of a Hymenaster which came up to-day there was a parasitic 

 Rhizocephalid, showing a large sucker and a flat body filled with eggs. I could not find any anus, and am not 



