13S 



Selections. [No. 7, new iehie*. 



This budding-cone is extremely productive, as one may often see 

 three or four rows of embryos in different stages thus coiled round 

 it, which when they have reached their proper size, separate them- 

 selves from it, and swim away as a chain. 



These single individuals are very rarely to be met with without 

 a chain of embryos round their cone, but here a most remarkable 

 circumstance comes in ; — during the time when the chained ani- 

 mals are still in an undeveloped condition round the cone, an egg 

 is formed on their surface which grows by degrees till it projects 

 into the gill-bag, and after a time becomes a separate individual, 

 though its stages of development have not been regularly traced. 

 This formation of an egg in an animal itself undeveloped, has 

 something in it most mysterious. 



However it may be it is certain that every kind of Salpce consists 

 both of chained and of single animals ; and that the single indivi- 

 duals produce rows of Salpoe, while the chained individuals pro- 

 duce one each which remains solitary during its whole life. 



There is but one family Salpoe, though several genera are proba- 

 bly yet to be discovered in it. 



There are no fossil representatives of the whole class of the Tu- 

 nicata. 



Sl7B KINGDOM OF THE MoLLTJSCA. 



Class of the Cephalophora. 



Sub-class of the Pteropoda. 



This sub-class consists of a few and insufficiently-known Mol- 

 luscs, which all distinguish themselves by wing-like projections on 

 the head which were at first supposed to be gills, but are really 

 only swimming organs composed of an endless number of crossed 

 muscular bundles. These little animals support themselves on the 

 surface of the sea by these swimming-flaps, and are very seldom 

 driven by accident into the neighbourhood of the shore. They are 

 all nocturnal animals, rising with the twilight in countless swarms 

 out of the depths of the sea, and sinking down again with the 

 morning light. The whole of the day not a brace of them is to be 



