ANCULA CRISTATA. 



development. The skin, though quite smooth and transparent to the naked eye, is found, 

 when examined under a microscope, to contain minute, crystalline, calcareous spicula, not 

 much crowded, and arranged without apparent order. They vary in size, and are cylindrical, 

 with the ends enlarged and rounded ; they are generally bent in the centre, but in this re- 

 spect there is considerable variation, some being arched or nearly straight, whilst others are 

 bent acutely in an irregular manner. 



This species was first described in the ' Annals of Natural History' under the name of 

 Polycera cristata, when the characters in which it differed from the typical Polycerse were 

 pointed out, and the propriety of establishing for it a separate genus suggested. It 

 approaches very nearly to Idalia, to which at one time we were inclined to unite it, but a 

 further knowledge of that genus convinced us that the present species ought to form a genus 

 distinct from either. We had consequently determined to raise it to that rank under the 

 name of Miranda, when fortunately we learnt by a letter from Professor Loven, of Stock- 

 holm, that he had already established for it the genus Ancula, in his i Index Molluscorum 

 Scandinavise.' This name, therefore, we now adopt, and are glad that the information came 

 in time to prevent our adding to the list of useless synonyms. It is interesting to know that 

 our species has been found on the coast of Sweden. 



The spawn is deposited on the under sides of stones in pools, chiefly in July, August, and 

 September, but not unfrequently as early as May or June, and occasionally as late as 

 November. The ova are imbedded without much regularity in a rather wide, transparent, 

 gelatinous belt, attached by one of its edges, and forming a single irregular coil. 



This species is found among the rocks near Cullercoats all the year round, but is 

 most abundant during the height of the breeding season, and is perhaps nearly as plentiful 

 as any of the nudibranchs on the Northumberland coast. When removed from the water it 

 has the appearance of an irregular globule, and might readily be mistaken for an 

 unorganized mass of gelatine ; but when again submerged the parts expand, and its true 

 nature is at once revealed. It moves very gracefully, but without much rapidity, and when 

 confined in a glass of sea water frequently swims on the surface. 



The heart pulsates from seventy-two to seventy-five times in a minute. 



Figs. 1, 2, 3. Ancula cristata in different positions. 

 4. Enlarged view of a branchial plume. 

 5, 6. Different views of a dorsal tentacle. 



7. Much enlarged representation of spicula. 



8. A portion of the skin, showing the arrangement of the spicula. 



9. Spawn. 



10. A portion of the same, exhibiting the arrangement of the eggs. 



