50 ILLINOIS BIOLOGICAL MONOGRAPHS [244 



in the interstices of which are large, broad cells acting as a framework. The 

 whole is very muscular and is turned and moved constantly. The position of 

 the mouth is noticeable. When closed, it is a very short slit at the anterior 

 ventral edge of the phar)mx. When fully open, however, the posterior corner 

 is drawn back ventrally as far as the connection with the intestine making 

 the whole pharynx bend downward. The opening itself is very large and con- 

 spicuous. The intestinal wall is rather heavy but otherwise the details of 

 structure are not strikingly different from other species of the genus. The 

 food is to some extent at least, composed of the eggs of other forms. In the 

 intestine of one specimen, eleven eggs of Typhlo plana viridata were found. 

 It was possibly true that these all come from a single individual which had 

 been swallowed bodily and the soft parts quickly digested. The heavy mus- 

 cular development together with such food masses seem to indicate a habit of 

 voracious feeding. 



The reproductive system is extraordinarily far forward with the single 

 genital pore nearly at the middle of the body. The two testes are long, slender 

 organs opening by a compHcated sac-like apparatus into the receptaculum. 

 The head portion of the spermatozoon is very large and is easily distinguished on 

 thru the wall of the vesicle. The ovary Hes a little to one side of the middle 

 and carries about ten eggs. In the younger stages it exhibits very many 

 small iridescent globules arranged in rows along the edges, where the eggs 

 touched each other. When the eggs leave the ovary, they pass down the short 

 oviduct to the uterus where, one at a time, they develop until they have a 

 diameter one-fourth that of the body. At maturity the egg is very conspicuous 

 because of its heavy wall and solid yolk mass, showing thru even the thickest 

 portion of the body mass. 



Altogether this species possesses rather notable individual characters. 



Six other species belonging to this family have been seen at different times, 

 but have not as yet been completely identified or described. The family is 

 very common in ponds both north and south. 



FAMILY TYPKLOPLANIDAE 



In 1831 Ehrenberg used the name Typhloplana for one of the twelve genera 

 which he described at that time as making up the new class Turbellaria. Five 

 years later he described the genus Mesostoma, which gave the family name 

 used until 1905, when von Graff outlined the general characters and gave 

 the distinguishing limits to the group. He then proposed the name Typhlo - 

 planidae from the oldest genus of Ehrenberg, for this new family, which in- 

 cluded only the old Eumesostomina and a few new genera described by Luther 

 (1904), The other parts of tlie Mesostominae Duges were made separate 

 families. The Typhloplanidae stand now as composed of three tribes, as 

 suggested by Luther, having two, six, and two genera respectively. Of all 

 the Turbellaria, this family is the best known. As von Graff says, the histo- 

 logical work of Luther and the descriptive work of several other writers have 

 made possible a really clear understanding of their morphology and biology. 



J 



