EFFECT OF SACCULINA UPON FAT METABOLISM OF HOST. 267 
The Effect of Sacculina upon the Fat Meta- 
bolism of its Host. 
By 
Guy C. Robson, B.A., 
Assistant in the Zoological Department, British Museum. 
With *2 Text-figures. 
Contents. 
page 
I. Introduction ...... 267 
II. The Effect of Sacculina upon the Lipochrome and Fat Supply 
of Inachus ...... 269 
III. The Nature and Function of the Lipochrome of Inachus . 275 
IV. A Note on the Origin of the Fat Supply of Inachus in Relation 
to Sacculinisation . . . . .276 
V. Summary ...... 278 
I. Introduction. 
The observations recorded in this paper were carried out 
in order to test a theory put forward by Geoffrey Smith 
(1), to explain the effect of the Rhizoceplialan parasite 
Sacculina neglecta upon the sexual physiology of its host, 
the spider-crab, Inachus mauritanicus. 
The effect of the Sacculina (2), stated briefly, is to cause 
the atrophy, partial or complete, of the generative organs, and 
to influence the external secondary sexual characters in such 
a way that the male tends to assume all the characters of the 
mature female ; while immature females prematurely acquire 
the adult characters of that sex. 
The theory suggested to account for this phenomenon was, 
that the Sacculina forced its host to elaborate a yolk-forming 
substance similar to that formed in a normal adult female 
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