STRUCTURE OF SEVERAL FORMS OP LAND PLANARIANS. ^ITI 



to be seen in section numerous longitudinal fibres of the internal 

 longitudinal set. 



The arrangement corresponds very nearly with that occurring 

 in Rhynchodemus ('Phil. Trans./ 1. c, PI. XI, 6g. 2), except in 

 the extraordinary development of the external longitudinal mus- 

 cular layer. 



Embedded in the inner muscular structures is an abundance of 

 a matter which appears to correspond to the glandular tissue of 

 Bipalium, and like it stains very deeply with carmine. In the 

 lower regions of the body it forms large ramifications. 



In the region of the body lying around the sheath of the pharynx 

 and that of the generative organs a glandular tissue is present 

 in great quantity, filling the interstices between the deeper 

 muscles (tig. 8, ^). 



The structure marked x in fig. 8 is evidently homologous 

 with the spaces present in Bipalium sections, which were con- 

 sidered to represent the primitive vascular system with the 

 nervous system probably lying in them ('Phil. Trans./ I.e., 

 PI. X, fig. 5, to). As in BipaUum these structures in the present 

 species stain very slightly with carmine. Instead of being con- 

 fined to two circumscribed areas in a vertical section, however, 

 as in Bipalium, or to two such areas connected by a transverse 

 link, the structures here assume the form of an irregular band 

 stretching across the entire width of the vertical sections. 



I have been unable to examine these organs in longitudinal 

 sections for want of sufficient material. I cannot come to any 

 certain conclusion as to what they represent, but think it pro- 

 bable that they may represent a diffuse and ill-differentiated 

 nervous system, since well- developed nervous structures such as 

 occur in Marine Planarians, such as Eurylepta, are certainly 

 wanting in all the genera of Land Planarians examined by me. 

 The portions of the structures in question, situate in the region 

 near the position of the oviducts (PI. XX, fig. 8, od), agrees in 

 histological construction closely with the homologous areas in 

 Bipalium, showing a fine reticulation of fibres whilst their con- 

 tinuations on either hand show a fibrillation in the direction of 

 the plane of the section, so that it would appear as if in the 

 region of the oviduct bodies of fibres and canals having a longi- 

 tudinal direction in the animaFs body were cut across, and that 

 these longitudinally directed cords or canals gave off transverse 

 branches, which appear in the sections as the horizonal exten- 

 sion of these lightly stained areas. As already described, a simi- 

 larly diffused nervous system or nervous system and primitive 

 vascular system appears to exist in the S. American Geoplanas. In 

 the present form it occupies a much wider space in the head of the 

 animal, just as in Bipalium ('Phil. Trans./ I.e., PI. XIV, fig. 7), 



VOL. XVII,— ,-NEW SER. T 



