of CalliopEea and on four new species of Eolis. 235 



The spawn of Doris tuberculata is a broad gelatinous riband, 

 attached by one of its edges to the underside of stones, in a cir- 

 cular coil of about three volutions, the whole forming a beautiful 

 cup- or flower-like expansion. The number of ova imbedded in 

 it, on a moderate computation, cannot be less than 50,000. Each 

 a^^ contains a single yolk, but frequently there are two, and 

 sometimes even three yolks in the same g^^. The period neces- 

 sary for their attaining the larva state appears to be about a fort- 

 night ; after that time the mass presents a very animated appear- 

 ance. When observed with a common magnifier, in some thd 

 full-formed larva will be seen whirling itself round with great 

 velocity in the transparent egg ; others, having broken the shell, 

 will be found performing more extended gyrations in the general 

 envelope, while others again are swimming hither and thither in 

 search of an aperture to escape into the open water. The larva 

 forms a beautiful object for the microscope. Its body is inclosed 

 in a very transparent calcareous nautiloid shell, furnished with 

 an equally transparent operculum. The whole surface of the 

 animal is covered with minute vibratory cilia, as are also the in- 

 ternal walls of the alimentary canal, which is visible through the 

 transparent shell. Two large wing-like lobes form the principal 

 part of the animal visible outside the shell ; these are fringed 

 with long cilia, by the motion of which it swims freely through 

 the water -, they are capable of being withdrawn into the shell 

 and the operculum closed upon them. The mouth is situated 

 between these lobes. It will readily be seen that these little crea- 

 tures do not bear even the most remote resemblance to the future 

 Doris. How long they remain in this state before their final 

 transformation, or how that takes place, we have not yet been able 

 to ascertain. The motion of these animals through the water by 

 means of ciliated expansions recalls to mind some of the forms of 

 the Rotifera, though sufficiently distinct from any of them. Com- 

 paring our drawings with those of Aplysia by Vanbeneden, we 

 observe a very striking resemblance between the two animals : 

 each has a similarly formed shell ; though that of Aplysia is stated 

 to be corneous, while ours readily dissolves in weak acids, from 

 which we infer its calcareous nature. We do not see in M. Van- 

 beneden's figures the expanded lobes so peculiar in these, nor, on 

 the other hand, can we trace in any of the parts of our animals 

 the least resemblance to a rudimentary head or foot. In addition 

 to that of Doris, we have succeeded in bringing out the larvse of 

 Eolisj Melibcea and Trifonia ; they all bear a very great resem- 

 blance to each other. 



The system of vessels pointed out by M. Milne E«rards in 

 Calliopeea, connected with the alimentary canal, and fcending 

 through the whole body, which he calls the gastro-vamular sy- 



n2\ 



