191 2. CoLGAN. — Development of Actaconia. 2.2"] 



was given to the variations in the head-appendages on this 

 occasion, as my efforts were directed chiefly to hatching 

 out the Actaeonia eggs. These efforts were not success - 

 fuL Although development proceeded up to the point 

 where the eyes appeared in the embryos/ none of these 

 succeeded in breaking free from the egg. 



In the next year, 1910, further specimens of Actaeonia 

 were taken in West Ireland on the shores of Clare Island. 

 A close stud}'^ of these, in a captivity which lasted from 

 the 20th July to the following 3rd November, show^ed that 

 the blunt head-appendages, which at the time of the taking 

 of the specimens in July, fully justified their assignment to 

 A. comigata, had so developed in a space of two months 

 as to equally justify their assignment to A. Cocksii. These 

 specimens laid three egg -masses with from 3 to 12 eggs 

 each, but though development proceeded quite as far with 

 these as with the similar egg-masses laid by the Bullock 

 specimens in the preceding year, in no case did the embryos 

 emerge from the Qgg. 



In recording the observations made on these Clare Island 

 specimens, it w^as hinted that A. corrugata might be nothing 

 more than immature A. Cocksii.^ These observations w-ere 

 in part suggested b}^ the doubts as to the distinctness of 

 the two species to which Sir Charles Ehot had given ex- 

 pression earlier in the same year in his valuable Supplement 

 to Alder and Hancock's Monograph of the British Nudi- 

 branchiate Mollusca} In this Supplement, how^ever, the 

 species were not fused, as the writer, having regard to the 

 peculiar development of Cenia Cocksii, demonstrated by 

 Pelseneer some twelve years previously, ^ and to the fact 

 that the development of the dubious A. corrugata was 

 quite unknown, thought it best to retain provisionally 

 the two species, and even to restore the genus Cenia, which 



1 The word " embryo " here and throughout these Notes is apphed 

 to all the stages of development of Actaeonia within the egg, since no 

 true larval metamorphosis takes place at any period. 



^ Proc. R.I. Acad., xxxi., Clare Island Survey, pt. 22, 1911. 



"^ Ray Society, 19 10. 



4 La condensation embryogenique chez un Nudibranche. Travaux 

 de la Station Zoologique de Wimeroux, vii., pp. 513 — 520. 



A.2 



