PLANARIA. 103 



exceeding the thickness of ordinary writing paper. On the upper sur- 

 face, towards the anterior, are four clusters of black specks. The orifice, 

 whence the proboscis protrudes, is situate far down the under surface. 

 In form, the animal gradually tapers downwards from its broad rounded 

 .anterior. Plate XIV. fig. 17., Planaria flexUis, back ; 18, belly ; 19, site 

 of the specks magnified, shewing their appearance and position. 



This Planaria does not yield to any of the tribe in voracity. It can 

 extract a Limnea of considerable size from the shell ; or sometimes in- 

 volving the living prey in the folds of its flexible body, carries it off' to 

 be devoured at leisure. It feeds so greedily as to endanger its own life, 

 a hump rising above with replenishment within. But all Planariae can 

 endure protracted abstinence, as is not uncommon among the Carnivora 

 in general, and their hunger is sated at indefinite periods. 



The chief season of propagation is in August, or during the preced- 

 ing and subsequent months. But it spawns occasionally at other times, 

 even in December. A single individual deposits a dull yellow stratum, 

 which tends to a quadrangular shape, and which consists of 300 or 400 

 ova, figs. 20, 21. Under the microscope, the ovum seems a spherical 

 capsule, divided into four compartments, as if investing four embryo 

 Planarice ; and some contain two or three globules besides, figs. 22, 23. 

 This division is less conspicuous in many ; and to judge by the progeny, 

 I have conjectured it to be an optical illusion. The embryo attains ma- 

 turity in about fourteen days, and when only one exhausts the whole 

 contents, and quits the ovum, it is not to crawl below like the parent, 

 but to swim at large in the surrounding element. * 



Patches of spawn, the ova being imbedded in slight albumenous 

 matter, were produced on the 1st of July. When subjected to the 

 microscope, two cross lines apparently divided the ovum into four com- 

 partments. On the ninth day, however, each ovum was discovered to 

 be occupied by only a single embryo, pursuing a slow horizontal course 

 around the interior circumferences. On the 14th, the ova had broken 

 up, when a multitude of corpuscular, or young Planaria) swam rapidly 

 through the water. These beings were of yellowish colour, broader and 

 more obtuse proportionally than the adult, fig. 24. A high magnifying 



