206 ZOOPHYTES. 



to the microscope. The spherules were gradually developing in a pris- 

 matic foi-m ; and one, as if elongating to its proper figure, deliberately as- 

 cending the side of the flask, issued head foremost from the mouth. But 

 it first hesitated there a moment, then dropped down through the water, 

 wherein its fall was sensibly retarded, as if by an invisible thread, and on 

 reaching the bottom, it glided swiftly away. In a few minutes, another 

 rising within the same flask, forsook it under similar circumstances : and 

 then a third followed after a short interval— PI. XXXVIII. fig. 10, a, b. 



The planula thus produced is very minute, not exceeding the sixth 

 part of the size of the single yellow planula from the ovate vesicle of the 

 red Sertularia — by which I mean in the quantum of matter. It is white 

 to the eye or grey in the microscope, the head obtusely rounded and about 

 twice the diameter of the opposite extremity, which is obtuse also. — 

 Fig. 11. 



The most prolific vesicles of fig. 10, contained about twelve spherules 

 indistinctly disposed in a double row. — Fig 12. But the contents of 

 others amounted to 24, 26, or even 30, imder similar arrangement.— 

 Fig, 13. A branch, scarcely half an inch long, bore fifteen prolific vesi- 

 cles, besides a sixteenth empty and transparent. No definite forms could 

 be discovered in the contents of some ; others contained irregular sphe- 

 rules, which, in several, were evolving into triangular prisms, denoting 

 progress towards perfect planulse, escaping from the rest. Fifteen em- 

 bryo planulse filled a vesicle, all losing their spherical form, which, along 

 with the contents, also discharged from another vesicle, during observa- 

 tion protracted an hour and a half, constituted a brood of 30 mature and 

 perfect subjects in whole. These animals did not surpass the third or 

 fourth of a line in length. No difference from the preceding which had 

 escaped from the vesicle just referred to, could be recognised except in 

 colour, these last being faint pink, while the preceding planulse were 

 white. They betrayed no activity, unless in quitting the vesicles, which, 

 correctly or not, was ascribed to the coldness of the day. Now the power 

 of a retaining filament was very evident. Everything would have sanc- 

 tioned the association of these creatures with the Planaria proper, in figure, 

 motion, and in habits. 



