442 Prof. Miiller on the Larval State and the Metamorphosis 



visible until we examine more minutely. It is first formed from 

 isolated figures with three arms, which are bifurcated and soon 

 form a lattice-work with circular meshes. At this stage of the 

 metamorphosis the larva swims about by its ciliary organs, which 

 remain in full activity, viz. the ciliary lines and the ciliary epau- 

 lettes, it creeps with its five feet, moves its pedicellarise like 

 pincers, and each spine separately. I have not had an opportu- 

 nity of tracing the metamorphosis of these larvae : the convex dis- 

 coid form of the new animal, its total dissimilarity from the As- 

 teri(B and Ophiurce, the numerous spontaneously moveable long 

 spines on the disc, and the three-limbed pedicell arise, leave 

 scarcely any doubt that it represents one of the Echinidce, but it 

 is impossible to say from these data whether it belongs to the 

 genus Echinus or Cidaris. 



To the same genus as that above described, in numerous spe- 

 cimens and in larvae seen several times almost every day, there 

 belongs also the larva of another species which resembles the 

 former in every respect, and especially in the ciliated epaulettes, 

 but which appeared to differ in the termination of the calcareous 

 axis in the dome ; for instead of the round dome, the summit 

 was conical and then truncated at the extremity. The calcareous 

 axes of the two anterior main arms of the larva projected into this 

 extremity and subdivided in the apex into two short oblique 

 branches. The position of the disc in the dome and its struc- 

 ture were the same as in the other species. 



My observations on the larvse of theEchinodermata with ciliated 

 epaulettes have proceeded thus far. To observe the complete de- 

 velopment of the Echinidce, it would be necessary to continue the 

 investigations through the first half of the winter. From obser- 

 vations on another species of larva which will be detailed here- 

 after, it is evident that the young Echinus has entirely lost all 

 traces of the larva even when the spinous part of its surface is 

 developed as far as a half of its entire sphere, and that the re- 

 maining part of the shell is subsequently perfected. As the sea 

 had become agitated and unfavourable to these investigations, it 

 must at present remain undecided whether the spinous surface 

 corresponds to the dorsal or ventral part of the Echinus, and 

 whether the five-limbed figure in the centre of this part belongs 

 to the genital plates with the anus, or, on the contrary, to the 

 dental framework and mouth. 



A third species of larva belongs to another genus of spinous 

 Echinodermata, probably also one of the Echinida. I have not 

 met with this species very frequently, but have traced it furthest in 

 its metamorphosis and up to that point at which the new spinous 

 spherical Echinoderm has lost all traces of the larva. 



These larvae, somewhat larger than the larvae of the Ophiura, are 



