230 GEOFFREY SMITH. 



was represented as changing from the katabolic male con- 

 dition to the more anabolic female, and this change was 

 supposed to be eifected by the development in tlie body of 

 the female sexual formative substance. It is clear that this 

 theory is fiuidamentaliy the same as that now proposed, but 

 being couched in lather vague and general language, it seems 

 to have made very little impression even on those who un- 

 reservedly accepted my statement of facts. By showing, 

 firstly, that tlie assumption of the adult female condition 

 involves an active elaboration of yolk material, and secondly, 

 that the Saccnlina roots actually withdraw some substance 

 from the crab's blood from wliich they manufacture a yolk 

 substance closely siuiilar to that normally deposited in the 

 eggs of the ci"ab, and also by emphasising the fact that in reality 

 both sexes of the host react in exactly the same way to the 

 parasite, it has been possible to express the theoiy in a far 

 more objective manner. 



Summary of Part 3. 



(1) The effect of Sacculina on male Inachus consists in 

 tlie assumption by the male of adult female characteristics, and 

 can in nowise be ascribed to arrest of development or acqui- 

 sition of juvenile or immature characters, as suggested by 

 Professor T. H. Morgan. 



(2) 'The effect of Sacculina on young immature females of 

 Inachus is to force them to assume prematurely adult female 

 characteristics. 



(3) The absorption of the gonad of infected Inachus of 

 both sexes is brought about by a process of eusheathment 

 with connective tissue and auto-digestion, phagocytosis ap- 

 parently playing no part. 



(4) The reason wh\^ Sacculina causes theassumption of the 

 adult female state in Inachus is found in the facts (1) that 

 the roots of Sacculina elaborate a yolk-substance from the 

 blood of Inachus of a similar nature to that which is elabo- 

 rated in the ovaries of an adult: female Inachus ; (2) that in 

 order to elaborate this yolk substance they take up from the 



