of Calliopsea and on four new species o/Eolis. 235 



Tlie spa-\ATi of Doris tuherculata is a broad gelatinous riband, 

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

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

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

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

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

 sometimes even three yolks in the same egg. 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. "N^Tien observed with a common magnifier, in some the 

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

 velocity in the transparent egg j 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, fm*nished 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 wdng-Hke 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 the water ; they are capable of being withdrawn into the shell 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. Tlie 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 cdiated expansions recalls to mind some of the fomis of 

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

 paring om- di-awings with those of Apli/sia by Vanbeneden, wc 

 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 om*s readily dissolves in weak acids, from 

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

 benedcn^s figm-es the expanded lobes so peculiar in these, nor, on 

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

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

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

 Eolis, Melibcea and Tritonia ; they aU bear a very great resem- 

 blance to each other. 



The system of vessels pointed out by M. Milne Edwards in 

 Calliopaa, connected with the alimentary canal, and extending 

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



R2 



