ANNULATA. 221 



belongs probably to the nervous system. In some species with 

 straight intestinal canal, there have been observed at the sides two 

 tortuous canals running longitudinally, which, without giving off 

 lateral branches, bend round in a loop at the back part. Respira- 

 tion is probably effected by the skin itself, and the water on the 

 surface is constantly renewed by the vibratory motion. 



As nervous system in many a double nervous ganglion has been 

 observed, which lies at the anterior end, and from which many 

 branches arise. The eyes, which are in some instances very nume- 

 rous, present in many a transparent body, corpus vitreum or lens 

 crystallina. 



The reproductive power is very great, and severed parts grow, as 

 appears from the observations especially of DUGES and J. R. JOHNSON, 

 to new animals. In some propagation occurs by spontaneous division. 

 The sexual organs have one common or two separate openings behind 

 the mouth; in the latter case the anterior opening belongs to the 

 male organs of copulation. Two long tubes supply the office of 

 testes, and end as vasa deferentia in a seminal vesicle, with which a 

 penis of various form is connected. The spermatozoa have been 

 observed by QUATREFAGES and YON SIEBOLD. A double oviduct 

 leads to a spacious vagina, into which two special hollow bodies also 

 open. The eggs lie dispersed in the parenchyme of the body, 

 between the ccecal branches of the intestinal canal (QUATREFAGES), 

 where probably they are contained in special ramified tubes 

 (ovaries). 



Compare on this family : 



YON BAER, Ueber Planarien. Nov. Act. A cad. Gees. L. G. not. 

 cur. Yol. xiii. P. 2, pp. 690 730. 



DUGES, Recherches sur Vorganisat. et les mwurs des Planariees, 

 Ann. des Sc. nat. xv. 1828, pp. 139 187 ; Observations nouv. sur 

 les Planaires, ibid. XXL 1830, pp. 7292. 



A. S. OERSTED, Entwurf einer systematischen EintJieilung und 

 speciellen Berschreibung der Plattwurmer. Mit Holtz-schnitten und 

 3 Tafeln. Copenhagen, 1844, 8vo. 



A. DE QUATREFAGES, Memoire sur quelques Planariees marines, 

 Ann. des Sc. nat. 3me Serie, Tom. iv. 1845, Zoolog. pp. 129 184. 

 PL 38. 



M. S. SCHULTZE, Beitrdge sur Naturgeschichte der Turbellarien. 

 Erste abtheilung. Mit Kupfertaf. Greifswald, 1851, 4to. also in 

 WIEGMANN'S Archiv. 1849. 290. 



