PLANAEIA. 90 



head and horns, together with much of the anterior portion of the body, 

 recovered the whole. This animal was of considerable size and of variegat- 

 ed colour originally, but the renovated parts were pale, and the horns small. 

 The cartilaginous proboscis of another, after separation, the effect of some 

 injury, testified vitality during three or four days. It would appear that 

 the peculiar texture of this organ is adverse to its indissoluble union with 

 this softer, more gelatinous, and perishable substance of the body. 



This is a prolific species of Planaria ; several hundred ova are pro- 

 duced in April, May, and other seasons, by a single individual. These 

 ova are minute, originally white, -then dingy yellow, and ultimately yel- 

 lowish-brown. They are always deposited in a single stratum, irregularly 

 disposed, but the stratum frequently tends to a rectangular figure, and 

 it is probably augmented at intervals. The side of a vessel is commonly 

 preferred. Fig. 1, spawn, enlarged. 



Notwithstanding the prospect of progeny from many parents I was 

 uniformly disappointed, and my disappointment so often reiterated, that 

 I despaired of success. 



Nevertheless my observations and researches were protracted during 

 two and twenty years, because perseverance can sometimes attain what 

 is denied to all other and more artificial modes of enquiry. 



On April 29, I procured a fine specimen of the Planaria cornuta, 

 which spawned soon afterwards. The spawn had been breaking up for 

 two or three days preceding May 24, when multitudes of extremely 

 minute yellowish specks were swimming in the water. Their motion 

 was sufficiently active, without being very quick ; it was pursued in all 

 directions ; and the spawn being contained in a small cylindrical jar, the 

 specks crowded to the side next the light, whereon numbers remained 

 almost stationary. 



Subjected to the microscope under a power magnifying sixty diame- 

 ters, they proved of very singular formation. About five short, obtuse, 

 rudely fashioned yellow rays, bordered a solid, compact, central, reddish 

 portion. Two of these rude like fingers seemed to belong to one part, 

 and three to that opposite. But the whole shape underwent variation. 



These animals left the field of the microscope so expeditiously, that 



