SEA-MA T MAKERS. 309 



adds, that " there can be no doubt that the ova 

 generated in the mother-cell (Zo&cium] do pass into 

 the ovicell, and there ripen into the perfect larva, 

 escaping at last through the orifice. The ovicell is 

 thus both a brood-chamber, and the passage for the 

 embryo from the cell to the surrounding water. But 

 whilst I have no doubt that the ovicell acts as a kind 

 of marsupium, there seems to me to be grounds for 

 believing that, in some cases and under conditions 

 which I cannot explain, ova are also produced 

 within it." 



The larvae, developed from the eggs, and which 

 are the units of a new polyzoan colony, are very 

 variable in form and complex in structure. They 

 *' are restless in their habits, and during their short 

 term of free existence, are in almost constant move- 

 ment now whirling rapidly hither and thither, now 

 tumbling over and over in the water, now creeping 

 along, making use of their cilia as feet. Besides their 

 ciliary appendages, they are often furnished with long 

 setiform processes, which wave to and fro, and lash 

 the water with much vehemence. After a while their 

 energies fail, and they settle down and become 

 attached ; the cilia begin to flag in their movements, 

 and soon disappear ; and the volatile, and curiously 

 organised being, resolves itself into a fixed and (ap- 

 parently) homogeneous mass, in which the first 

 polyp-cell (ZocEciiuri) and polypide originate." 



