5Ö2 



Memoirs of the Indian Museum. 



[Vol. V, 1921.] 



The differences noted in the specimens were confined to the size and shape of the pit. 

 In one or two specimens a constriction appeared immediately behind the anläge of 

 the head; separating the worm into two parts (fig. a). 



Remarks. — There can be no doubt that the parasites are Plerocercoid larvae. It 

 is impossible to identify or classify them at this stage of their development. 



a/. O. 



Text-figure, i. — Plerocercoid larva from Acromitus rabanchatu. 

 a. Outliue of a larva showing construction behind the head x 69. 

 b. Entire worm in optical section x 69. 

 c. Oblique section through anterior region of larva x 143. 



As far as I am aware, no Cestode larvae have been recorded previously from 

 animals so low in the zoological scale as Medusae. 



It would appear probable that the chances of these larvae becoming adult worms 

 are practically nil, for I know of no animal which feeds on jelly-fish. We may thus 

 regard their occurrence in Medusae as representing a cul-de-sac in their life-history. 



