OF ARTS AND SCIENCES: APRIL U, 1863. 107 



stant than when young. The anal portion is kept in advance when 

 moving, and the larva rotates about, but not as frequently as when 

 young ; moving more generally with either the ventral or dorsal side 

 uppermost, and more rarely in such a way that the profile can be seen. 

 When at rest, they invariably assume one and the same position ; that 

 is, turn slightly obliquely below the anal portion, with the dorsal 

 surface downwards. In this way they often remain for a long period, 

 simply carried about by the currents ; the only movements being the 

 expansion and contraction of the oesophagus, and the slow bending 

 and twisting of the arms in every direction. 



Up to the stage represented in Fig. 9, all the larvte were raised 

 by artificial fecundation from eggs of Asteracanthion berylinus Ag. At 

 the time when I discovered these larvaj I immediately examined 

 the ovaries of our star-fishes, and found that in one species, the heryli- 

 nus, the eggs were not yet sufficiently advanced to be fecundated, while 

 the eggs of the second species, which is so common on our rocks, 

 the Ast. paUidus, had all escaped. I had, however, been fortunate 

 enough to find quite young larv^ of this second species in which the 

 water-tubes were still exceedingly small, and had made a complete 

 series of drawings of general outlines from their youngest stage up 

 to the time when the star-fish is formed, so that I am certain that 

 all the young I have represented as belonging together are those of 

 one species, as the interval between the time when these two species 

 spawn is more than three weeks. 



The time of spawning is very short ; three or four days after the 

 Ast. berylinus began to spawn it was quite difficult to find females 

 which had not lost their eggs, and a week after that period I found 

 none. Owing to this great difference in the time of spawning, and 

 its short duration, the dates at which I caught these star-fish larvae 

 floating about leave no doubt to which of the species the larv^ be- 

 longed. A careful comparison of the youngest specimens also shows 

 very striking differences, which will always enable an observer to dis- 

 tinguish readily the larva3 of these two species, even in their earlier 

 stages. 



The males can easily be distinguished from the females by their 

 difference of color ; the females being always slightly bluish, while 

 the males have a decidedly reddish tint. The same difference in color 

 is noticed in our Sea-urchin, Toxopneustes drohachiensis. The fe- 

 males are of a light green at the time of spawning, while the males 

 are of a dull vermilion color. 



