Manchester Memoirs, Vol. Ixv. {1921), No 11 



XL On the Coral-Gall Prawn Paratypton. 



By L. A. Borradaile, M.A., 



Fellow and Tutor of Selwyn College, Cambridge, and 

 Lecturer in Zoology in the University. 



(Communicated by W. M. Tattersall, D.Sc.) 



(Read March 22nd, 1921. Received for publication May 10th, 1921). 



There is no task more fascinating to the naturalist than 

 breaking up a block of some branching coral, such as 

 Pocillopora or Madrepora, and dislodging from among its 

 boughs the various animals that shelter there ; nor of all these 

 latter is there any more interesting than the crab Hapalo- 

 carcinus, which gives rise to the well-known galls that Semper 

 described in his " Animal Life." This organism has recently 

 been very thoroughly investigated by Potts. 1 He has shown 

 how the female settles in the fork of a young branch while she 

 is still very small and immature ; how by her gill-stream she 

 directs the growth of the coral so as to mould it around her 

 into a gall, which eventually closes, leaving only a row of little 

 openings through which the stream flows in and out; how 

 meanwhile she is undergoing the changes by which she 

 reaches the adult condition, with a large, soft-bordered 

 abdomen enclosing as in a pouch below the cephalothorax the 

 limbs which bear the eggs ; how midway in this development 

 she is visited by the male, which is free-living and smaller 

 than his mate was even at her first settling ; how she feeds on 

 the minute organisms (nannoplankton) brought to her by the 

 stream of water which she draws through the gall ; how her 

 mouth-parts are modified in correspondence with this, the 

 slender endopodites of the maxillipeds of the first pair and 

 the exopodites of the second and first having long fringes, 

 presumably for gathering the food much as does the China 

 Crab Porcellana, and the inner mouth-parts being greatly 

 reduced in the absence of the need for much mastication ; and 

 how, finally, she would appear to lay, after one impregnation, 



1. Carnegie Institute, Washington, 1915, 212. 



November ioth, iQ2i. 



