50 Mr. E. A. Minchin. Note on the Larva and the 



FIG. 7. Optical section of larva of L. reticulum, first day, x 500. 



difficult to follow, but in both immigration appears to take place 

 from any point on the surface. 



In L. cerebrum and L. reticulum the larva swims for about 

 twenty-four hours at the surface, and as long at the bottom, and fixes 

 on the third day. L. coriacea, on the other hand, is remarkable for 

 its abbreviated larval period as compared with the two Mediterranean 

 species, since the larva fixes in a few hours, a fact doubtless in con- 

 nexion with its life between tide marks, where the violent currents to 

 which it is exposed renders a very sheltered, and therefore limited, 

 habitat necessary for so delicate an organism. 



After fixation, the larva undergoes changes whereby the ciliated 

 cells become surrounded by the formerly internal granular cells, so 

 that the ciliated external layer of the larva represents the gastral 

 layer of the adult, while the inner mass becomes the dermal layer ; 

 the reverse of what was supposed by Metschnikoff and Schmidt (loc. 

 cit.) to take place. 



In L. cerebrum I was able to observe the first appearance of the 

 spicules. As in variabilis, the complete metamorphosis results in a 

 stage in which the gastral cells form a compact internal mass, snr- 



