245 



different order. Furthermore, on the very same species of Spirontocaris (Hippo- 

 lyte), S. securifrons, and at about the same place, below the anterior part of the 

 tail, may be found sometimes a Bopyrid (Phryxus), sometimes a rhizocephalic Cirriped 

 (Sylon), and the same species is very often found to be infested by another Bopyrid 

 (Bopyroides). A similar case is also shown in our common hermit crab, Eupagurus 

 bemhardus. It may be found infested by a Pseudione under its carapace, or it 

 may carry on the dorsal face of its tail a very different Bopyrid, Athelges, and 

 the place of the latter is not infrequently occupied by a rhizocephalic Cirriped Pelto- 

 gaster, to which again sometimes a Liriopsis is found attached. There is nothing 

 that forbids the assumption, that the Amphipoda may also be infested by para- 

 sites of very different nature, and indeed Dr. Hansen has shown that they not 

 infrequently contain in their marsupium Choniostoniatidce belonging to 2 different 

 genera, Stenothocheres and Sphosronella. As to the Cryptoniscid in question, 

 there is a circumstance, which makes it rather improbable that it should be 

 transformed to a Podascon. One of the specimens, the one here figured, was 

 found, on a closer examination, to be provided with very fully developed ovaries 

 in the form of 2 dark-coloured bags extending through the greater part of the 

 mesosome, and containing a restricted number of comparatively large ovarial 

 eggs. In no other instance have I found the ovaries in this stage developed to 

 such a degree, and this seems to indicate that the metamorphosis of the present 

 form might be far less complete than in other Epicarids. Perhaps we even have 

 here an instance of the female retaining its larval characters also in the adult 

 state. In this connexion it is worthy of note that the present form is of 

 considerably larger size than any other larval stage of Epicarida with which I 

 am acquainted. 



Occurrence. — The specimen examined by the Rev. Th. Stebbing was found 

 among the ova in the marsupical pouch of an Onesimus plautus Kroyer, taken 

 in the Barents Sea. I have myself found it under altogether similar circumstances, 

 and on the very same host at Bodo, and have also occasionally taken it off the 

 Nordland coast free in the sea by the aid of the tow-net. The same form also 

 occurred in some Plankton-proofs taken during Nansen's Polar Expedition in the 

 glacial sea, north of Siberia. 



From the above mentioned finding-places, it seems to be a true 

 arctic form. 



