Bibliography. 3 



at the point where the adult Sacculina is definitely attached. Delage fills in this lacuna by 

 the very just inference that the cells of the Cypris larva, after reaching the blood system of 

 the crab wander through the body establishing the root system, and finally, on reaching the 

 intestine at the junction of thorax and abdomen, forni the body of the Sacculina interna which 

 he found at various stages of development in this position. 



Before Delage's discovery it must be remarked that no one knew that the parasite passed 

 through an internai stage at ali. It was generally supposed (e. g. Kossmann) that the Cypris 

 larva fixed itself upon the abdomen of the crab and became transformed in situ into the adult 

 animai. Giard in fact suggested that he had seen the parasite in process of development at 

 this point, a pretended discovery which wasted a great deal of Delage's time, so we are told, 

 and drew from him a decidedly caustic criticism. (Loc. cit. p. 557.) 



Besides observations on the fixation and internai stages, Delage rediscovered the larvai 

 males of Fritz Muller, and affirmed that they are always present to the number of 1 — 12 

 attached to the mantle-opening of Sacculinae which have recently become external. He never 

 succeeded in observing more than the dead cuticle of these larvae, a failure shared by ali 

 previous observers. But Delage, from their invariable occurrence , utterly repudiates Giard's 

 suggestion that they are only ordinary larvae fixed there by accident, and he accepts Mìjller's 

 interpretation of them as larvai males. Finally, with regard to the effect of the parasite on 

 the host, Delage criticises unfavourably the suggestions of previous authors, dismisses, curiously 

 enough, Giard's observation as to the sterility of the host effected by the parasite, and states 

 that the chief effect is that the crab is inhibited in its growth and prevented from moulting. 



In this short review we have only touched on controversial questions and have not 

 pretended to give a complete summary of Delage's masterly memoir, to which further reference 

 will frequently be made. Delage's account of the fixation and internai parasitism of Sacculina 

 has been generally accepted and incorporated in ali the standard text-books, but there has 

 been one dissentient, loudly dissentient, voice. Professor Giard (16) in 1886 published a note 

 in the Comptes Rendus entitled "Sur l'orientation de la Sacculine". He here finds fault 

 with Delage's explication of the asymmetry of the adult Sacculina and reaffirms his own, with 

 the criticism that Delage's view is influenced by his preconceived idea that the position of 

 fixation of the Cypris larva cannot affect the symmetry of the adult. He suggests that Hesse 

 in 1866 had seen and recognised Sacculinae internae and that ali the world had seen them 

 as well as Delage: he next denies that Sacculina is ever really internai, and supposes that it 

 only appeared so to Delage owing to his brutal method of tearing out the intestine of the 

 crab: finally he records his conviction that the fixation of the Cypris larvae described by 

 Delage is purely abnormal and that the true method of fixation is locai upon the spot where 

 the parasite becomes adult. The only new observation of fact which Giard makes in this 

 criticai note (it is used as an argument against Delage) is that Sacculina neglecta only infects 

 the female of Inachus scorpio, a statement which he withdraws in a subsequent note. In this 

 succeeding note (18) Giard makes his first observation upon the highly interesting phenomenon 



