StRUCTURE OF SEVERAL FORMS OF LAND PLANARIANS. 291 



and tropical regions, and probably exist in all. They may be 

 placed in two families : 



{a) Leimacopsidse, with eye-bearing frontal tentacles. 1 genus. 

 1 species at present known. 



(b) Geoplanidse. Without tentacles. 7 genera. 62 species. 



The structure of Leimacopsis is not known, but it seems 

 probable that it may differ very much from that of the Geoplanidse. 



Of the Geoplanidse, the complete anatomy, including that of 

 the generative organs, is known as yet only in the case of certain 

 species of Ehynchodemus, and Bipalium from Ceylon, and in 

 Geoplana Traversii of New Zealand. The arrangement of the 

 muscles and of the lateral organs (nervous systems, or primitive 

 vascular systems ?) of the Rhynchodemus of the Cape of a 

 Geoplana of Brazil, of the Austrahan Ccenoplanas, and Manilla 

 Dolichoplauas, has been determined, and it appears that the 

 Geoplanidse form a very natural family, although it remains to 

 be seen how far the European forms at present placed in the 

 genus Rhynchodemus conform to the type. In all the Geoplanidse 

 the external sets of circular and longitudinal muscles are more 

 fully developed than in the aquatic species in conformity with the 

 requirements of motion on land. In Geoplana and the Australian 

 genus this condition is more marked than in Rhynchodemus 

 and Bipalium, and is carried to excess as far as the longitudinal 

 bundles are concerned in Dolichoplana, in which form loco- 

 motion is probably principally muscular and annelid-like. In 

 all the Geoplanidse further the generative organs show a ten- 

 dency to specialisation higher than that of most aquatic forms. 

 In Geoplana Rhynchodemus and Bipalium, and in Poly- 

 cladus, as appears from Blanchard's figures (Blanchard, Hist, 

 de Chile, 1. c), the ovaries are reduced to small simple piriform 

 sacs, which are placed near the anterior extremity of the body, 

 and have long simple oviducts leading for more than half the 

 length of the body to the uterus. This condition is conformed 

 to even in the enormously long Dolichoplana. The intermittent 

 organs and reservoirs are closely similar in all the genera 

 examined. The Geoplanidse are all monogonoporous. In all 

 the uterus is simple and situate just posteriorly to the penis. 

 The highest specialisation of the generative organs appears to 

 occur in Bipalium. In the concentration of these organs and 

 special development of the muscular systems the Geoplanidse 

 seem to form a step from the aquatic forms towards the leeches. 



Prom the facts of anatomy, at present ascertained, it appears 

 that the New Zealand forms are most closely alHed to the S. 

 American, whilst the Cape species are related to the Indian land 

 planarians — a conclusion which is borne out by other facts of 

 distribution of species. The Australian Ccenoplanas form a step 



