TURBELLARTAN WORMS 



3443 



chance of escape. It is stated that this and other species insnare their prey 



by means of slimy threads. Eggs of two kinds are laid; those found in summer 



being soft shelled, while those of winter are protected by a hard and thick coat 



so as to be able to withstand the unfavorable conditions of this season. An allied 



species (M. tetragonum) is shown in the accompanying illustration. Upon 



the narrow and pointed head are the two little black eye-spots. In the 



genus Prostomum the mouth (b) is situated in the middle of the ventral surface, 



as in the last, but the slender 



and pointed head end is 



provided with a distinct 



proboscis (a), which calls 



to mind that of the 



nemertines, inasmuch as it <j> 



is not directly connected 



with the mouth, and is 



contained in a special sheath. 



The posterior end of the 



body, on the contrary, is 



thick, club shaped, and 



armed with a sharp goad, 



which seems to be used as 



i. Prostomum 



TREMATODES. 

 . proboscis ; b. mouth. 2. Convoluta. 3. Vortex. 



(Natural size represented by lines.) 



an organ of defense. The 



same illustration shows a 



species of the allied genus Vortex, in which the aperture of the mouth is on the 



under side, near the front end of the body. This mouth leads into a large oval 



gullet, communicating with the long sac-like intestine. The black spot in front 



of the mouth is the eye. In Schizostoma, on the contrary, the mouth which is 



long and slit-like, is situated in front of the two eyes. Some of the allied genera 



Schisostoma productum (enlarged 200 times.). 



lead a parasitic and not a free life. For instance, Anoplodium is found upon sea 

 cucumbers, and Graffilla upon marine gastropods. 



Differing in many important points from the typical Rhabdocoela is the small 

 marine Convoluta, shown in Fig. 2 of the illustration, in which the alimentary 

 canal, the excretory organs, and the nervous system have disappeared. Imbedded 



