19^2. CoLGAN. — DcvdopmeJit of Aclaconia. 231 



ova became visible through the transhicent foot as the animal 

 floated on the water-surface. By the 5th May, the largest 

 individual had grown to a length of 4 mm. ; the pellucid 

 visceral hump had become prominent, and through it the 

 valvular action of the heart could be watched, while the 

 head-appendages had assumed the tentacular form charac- 

 teristic of A. Cocksii. The last of the young Actaeonias 

 died on the nth May, 191 2. Originally twelve in number 

 when hatched out on the 20th March, they had by the ist 

 May diminished to four, partly by death, but chiefly by 

 loss in transferring from stale to fresh water. 



As an instance of the vitality of the species it ma}' be 

 mentioned that the severed head of an individual just 

 one month old, accidentally decapitated on the 17th April 

 in the endeavour to detach it from the Cladophora to which 

 it clung, lived for 7 days and a half. At gradually lengthen- 

 ing intervals throughout this period the lips, without any 

 outer stimulus, continued to make automatic motions as 

 if in the act of feeding, while the head travelled through 

 the water by the action of its epidermal ciha. When quies- 

 cent, the least stimulus, even the jarring of the dish in which 

 the head floated, was sufficient to set up these mnemic actions 

 of the mouth, reminiscent of its habitual motions while yet 

 attached to the body. 



Accepting as proved the identity of Actaeonia corrugata 

 with A. Cocksii the name to be borne by the species remains 

 to be considered, The generic name presents no difficulty, 

 since Actaeonia has clearty priority over Ccnia. It is 

 otherwise, however, with the specific component, as both 

 of the species here combined were simultaneously published 

 (in the June number of the Annals and Magazine of Natural 

 History for 1848). Under the Nomenclature Rules and 

 Recom.mendations it would appear to be open to the reviser 

 in such a case as this to adopt whichever name he may 

 think fit. I accordingly fix on Actaeonia Cocksi^, and for 

 this reason, chiefl3',that the original description and figure of 

 Actaeonia (Cenia] Cocksiv^-ere taken from, a mature individual. 



Sandycovc, Co. Dublin. 



1 In accordance with the Rules I drop here the redundant " i " in 

 the latinized form of the discoverer's name. 



