86 DR. COLLINGWOOD ON THIRTY-ONE 



spherical body (crystalline), surrounded with pigment ; and they are always situated in a 

 part which is free from the usual pigmentary matter of the animal, and where the skin 

 is reduced to a minimum of thickness (Baer). In any case they can but very imperfectly 

 perform the function of vision ; and in one family (Typhlolepticlse) they appear to be 

 altogether absent *. Nevertheless these animals all seem to avoid the light, by concealing 

 themselves under stones and in situations where no light can reach them. 



Their ova are deposited in thin flakes upon sea-weeds and stones, and in appearance are 

 not unlike those of the Nudibranchs, for which at first sight they might be mistaken. 

 They resemble these mollusks also in their habit of floating, back downwards, upon the 

 surface of the water. Nor do the resemblances end here ; for some genera of the Eury- 

 leptida? are provided with numerous papillse, more or less covering the whole upper sur- 

 face, after the manner of an JEolis, which character earned for them the generic name 

 of JEolidiceros from De Quatrefages. 



It has often been said, and is copied from one book into another, that these animals 

 have the power of spontaneous fission, by means of which two individuals are produced 

 from one. I can only say that, of the numerous specimens I have met with, kept alive, 

 and carefully watched, I never saw any thing like this process take place in any instance. 

 Still I cannot assert that it does not happen. 



It is worthy of remark that among the 19 species of Dr. Kelaart, no less than 11 

 appear to be referable to the genus JEurylepta (Hemp, and Ehrenb.), while of my own 12 

 species only one is of that genus. Not one of Kelaart's claims rank under Quatrefages' 

 old genus JProceros, in which one fourth of my own species occur. In each collection is 

 found a new genus of Euryleptidse ; and the whole of the 31 species are included under 

 one sub tribe — Digonopora, or monoecious Turbellaria. 



II. 



(Characters of two new genera of Eurylepidae.) 



TUKBELLAMA DENDROCCELA. 



Genus Acanthozoon, Coll. 



Caput subdiscretum, tentaculis parvis approximatis. Corpus supra spinulis brevibus nigris ubique 

 instructum. 



Thysanozoon, 



Acanthozoon, JProceros, 



Eurylepta. 



Genus Sphyngiceps, Coll. 



Corpus lseve, caput discretum, tentaculis magnis subdistantibus ; ocelli occipitales et capitales. 



JProceros, 

 Sphyngiceps, 



JEurylepta. 

 * "With, regard to the eye-spots, structurally and as supposed organs of vision, consult H. N. Moseley's remarks 

 thereon, " Anat. and Histol. Land-Planarians of Ceylon," Proc. Roy. Soc. 1873, p. 172 &c. 



