82 Memoirs of the Indian Museum. [Voi<. I, 



so thatj although these animals are very desirable as museum acquisitions, it seemed 

 well to spare one of them for dissection. In anticipation of this, one specimen was 

 treated in the following way : After making numerous small slits in the soft cuticle 

 between the segments, and puncturing the eyes, the animal was deposited in 2 per cent, 

 formalin solution for 48 hours ; from this it was transferred to strong spirit. The 

 dissection was performed six months later, when the tissues were found to be 

 in such good condition that even histological detail could be made out with some 

 satisfaction. 



The example dissected was an immature female measuring 193 mm. in length 

 and 89 mm. in breadth, to which standard all measurements of internal „organs may 

 be referred. The description is unfortunately incomplete. Before describing the 

 internal organs of any animal, the dissector should examine several specimens 

 Doubtful points arise in a first dissection, which ought to be confirmed by subsequent 

 examination of other specimens. Only those points which were clearly observed 

 have been described here ; the doubtful points have been left as gaps in the des- 

 cription. Besides this, certain special difficulties were met with in this case. On 

 opening the carapace mid-dorsally, the most noticeable feature was a mass of eggs. 

 These eggs were nearly of the mature size (scarcely less than i cm. in diameter) ; 

 they did not seem to • form part of well-defined ovaries, but lay above and between 

 the other organs, being shaped irregularly to suit their surroundings. They were 

 of a resinous colour, somewhat translucent and very hard, and were imbedded 

 in a white, fatty material. This condition was probably brought about by the 

 bursting of the limiting membrane of the ovaries, at the time when the animal 

 was removed from the pressure of its native depths. Whatever the cause, yolk 

 material of resinous appearance was found, even below the intestine and between 

 the lobes of the hepatopancreas, and caused considerable trouble in elucidating the 

 anatomy. 



Let us pass, now, to a consideration of the previous work done on the internal 

 anatomy of Isopods. Among the group several types have been described in this 

 respect. The internal anatomy of land genera, such as Armadillidium, Oniscus, 

 Porcellio and Ligia has been amply described by Lereboullet and other observers (4 — 9). 

 Asellus has been fully treated by Sars and others (10, 11). Several of the smaller 

 marine genera have been investigated (12, 13). These descriptions show that the 

 different genera of smaller Isopods are, on the whole, similar in their soft parts. 

 As to its internal anatomy, Bathynomus is found to differ from those genera in several 

 important respects. Unfortunately, I have not been able to find descriptions of the 

 internal organs of the Circlanidce , which might be expected to resemble Bathynomus 

 more closely. 



■^tt would seem, however, that, merely owing to its size, Bathynomus must be 

 different in certain respects from all smaller members of the group. Thus, consider 

 for a moment, the structure of the hepatopancreas. In a small Isopod such as 

 Asellus, this organ consists of two pairs of tubules extending almost the whole 

 length of the intestine, and occupying to a great extent the space between that 



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