TURBELLARIA DENDROOELA. 



315 



FIG. 251. Larva of Euryleptn auri 

 cidntd, after Hallez. 



probably the function of tactile organs. The mouth usually lies 

 in the middle of the body, and leads into a wide and protrusible 

 pharynx. The skin is often provided with glands, the secretion 

 of which in certain land Planaria (Bipaliwm,, Rhynchodesmus) 

 hardens to a fibrous web. They are almost always hermaphrodite. 

 The fresh-water forms possess a common 

 generative opening, while in the marine 

 forms the generative openings are usu- 

 ally separate (fig. 250). In the latter 

 case a separate vitellarium is absent. 

 In some marine forms development 

 takes place with metamorphosis, as is 

 shown by the larva discovered by J. 

 M tiller, which possessed six provisional 

 finger-like ciliated lobes (fig. 251). 

 In the fresh- water Planarians develop- 

 ment is direct. The cocoon, when laid, 

 contains four to six small eggs. At the 

 close of segmentation there is developed 

 a layer of cells, which is said to split 



into two layers, an upper or animal layer, from which are derived 

 the body wall and muscular system, and a lower or vegetative, from 

 which the alimentary canal is formed. The marine Dendroccela fre- 

 quently deposit their eggs in the form of broad bands. 



1. Monogonopora Stimps. Den- 

 <lr<>c<>:l with single sexual opening. 

 The land and fresh-water Planaria be- 

 long to this group. 



Fam. Planariadae. The body is of a long, 

 oval, flattened shape, and is often provided 

 with lobed processes, more rarely with ten- 

 tacles, and. as a rule, with two eyes, which 

 are provided with lenses. PLtnuria O. Fr. 



P r, Miiller. two eyes, no tentacles. PL turrit. 



M. Sch. (divided by O. Schmidt into li///ntiri*- 

 FIG. 252.Plannriii jiofychroa (c), jmli/cJirtnl. and turn/') (tig. 252). PL (Jiinrti 

 liignbri* (I), toi-va (c), about twice f<j a p w }th separate sexes. 2>< nilr<><-ii']//in 

 the natural size (after O. Q Distinguished bv the possession of 



Schmidt). 



lobed processes on the head, also by the 



presence of a copulatory organ placed in a special sheath. U. lin-ti'iiin Oerst., 

 Poli/ci'lix iiii/rd. lirtinni-a 0. Fr. Mull. 



Fam. Geoplanidae.* Land Planarians. They are characterised by their 



s Besides M. Schultze. Stimpson. Metsclmikoff. Grube. etc.. compare H. N. 



