A. E. Verrill — Marine Planarians of N'evi England. 4-71 



branches of the stomach, or to the reproductive organs, vary accord- 

 ing to the kind and quantity of food, the season of the year, etc. 

 Hence the forms and colors are usually of secondary importance 

 in distinguishing the species and genera. 



The form and structure of the i-eproductive organs are here of 

 the greatest importance, but these organs can usually be seen 

 only very imperfectly, if at all, unless the specimens are preserved 

 and mounted in such a manner as to render them translucent.* A 

 few species are sufficiently translucent while living, especially when 

 immatui'e, to afford a fairly good view of their internal organs when 

 slightly compressed between glass, especiall}^ immediately after they 

 are killed with some agent that does not coagulate the fluids of their 

 bodies. f The structure of the pharynx and the number and modes 

 of division of the main branches of the stomach affoi'd characters 

 of great value that can be easily observed. 



I have good reasons for beliving that there ai"e a number of 

 species of this group living on our coast, that are not included in 

 this article. This is doubtless largely due to lack of attention to 

 this family on the part of collectors, myself included, owing partly 

 to the prevalent impression that all the forms are members of one 

 or two common species. I have observed young specimens of 

 several kinds, too immature to describe specifically, that are evi- 

 dently not the young of any of those here included. 



Leptoplana (Ehrenberg) Lang, (restr.). 



Polycelis {jjars) Quatrf., Ann. des sci. nat., ser. .3, vol. iv, p. 133, 1845; Voyage 



en Sicile, ii, p. 33, 35. 

 Leptoplana and Elasmodes {2mrs) Stimp., Prodromus, p. 3, 1857. 



' Body foliaceous, usually with thin undulated margins, usually 

 elliptical or oblong, changeable. Ocelli numerous, forming four 

 groups : cerebral and dorsal. The anterior or cerebral ones are sit- 

 uated over the cerebral ganglions, the dorsal groups occupy the 

 position of the teiitacles found in Planoceridce. No marginal ocelli. 

 Phar^'nx with more or less numerous broad, short accessory lobes. 



Genital pores rather widely separated, the male pore distant from 

 the posterior end of the body. Female pore opens backward and is 



* It must be noted that the form and relative positions of these organs are more 

 or less altered by all modes of preservation, owing to contraction of the tissues. 



■[ I have found hydrogen peroxid an excellent reagent for this purpose. Nitric 

 acid often does very well, as do many other agents in common use. Alcohol, corro- 

 sive sublimate, chromic acid, etc., render the tissues more opaque. 



