jfovertebrata. Zoological Collections, S'/V 



exaggerated : thus, the inferior portion of the body never produces an entire 

 individual, as has been said : the brain divided into two by a longitudinal 

 section, which would separate the first rings, does not give origin to two 

 heads, &c. The anterior part of the body alone, when cut at a certain 

 distance from the clitellum, reproduces a posterior part; or the rings, bristles, 

 and other organs which belong to the normal portion. This is also the case 

 with the lips. M. Morren also states, that several individuals may be 

 soldered together. 



Observations on the Planarice and several neighbouring genera. By M. Ant. 

 Duges. — The genus Prostoma, which M. Duges has established for ani- 

 mals, partly new to naturalists, and partly confounded with the Planaria:, 

 has been adopted by MM. Cuvier and De Blainville ; but the latter sepa- 

 rates it from the family of the Planariece to join it to the Nemertes, &c. and 

 this transposition is entirely approved of by M. Duges. 



M. Duges was at first acquainted with only one species, Prostoma clep- 

 seno'ideum ; he has since found three others, one of which had, however, been 

 previously known as a Planaria. These species are, — P. lunibricoideum, 

 inhabiting brooks; P. candidum, {Planaria Candida, Miiller;) andP. armatum, 

 in the MediterrancHn. 



Oil this last species, M. Duges has been enabled to extend his anatomico- 

 physiologieal investigations, from the facility with which its body yields to 

 compression. Thus, he has observed, that the exsertile portion of the 

 mouth is furnished with two groups of hard points, (three in each group,) 

 and, in the centre, with a horny process, terminated by a sharp point or dart. 

 The groups of points probably serve to retain the Annelides, on which the 

 Prostoma preys, and the dart to pierce them. M. Duges could also observe, 

 in the Prostoma armatum, a complete circulating system in the whole extent 

 of the body. In the reproductive apparatus, the Prostoma presents peculia- 

 rities worthy of remark. All along the sides of the body is a series of 

 pouches with a narrow neck, opening externally, and capable of being pro- 

 truded by compression. In the Prostoma lumbrico'idenm these pouches 

 enclose from three to four vesicles, containing a pulpy substance, and a 

 transparent point or globule. This singular disposition reminds us of the 

 ovaries of the Tcenia, which have an opening externally for each segment of 

 the body. 



The genus Derostoma, well characterized by an unilocular alimentary- 

 sac, visible through the skin, with a single opening always inferior, ought, 

 according to the observations of M. Duges, to be divided into sections 

 according to the situation of the mouth. Some, indeed, and the greatest 

 number, the Derostomata proper, have this orifice situated near the anterior 

 extremity ; others have it, like the Planarice, in the middle of the body, 

 although they differ from these animals in the absence of an exsertile trunk, 

 in the simplicity of their digestive cavity, and in their more or less cylindri- 

 cal form. M. Duges calls his second section Mesostoma. 



To the first section belong D. notops, leucops, squalum, lanceolatum, platumm, 

 poli/gastrum, described in a previous memoir of the author. To these must be 

 added the following species, described by M. Duges as new : — D. mutabile, 

 angusticcps, selenops, truncatum, {Planaria truncata ? Miiller,) griseum {Plana- 

 ria grisea ? Miiller,) and megalups. This last is the largest of the Derosto- 

 mata which M. Duges has met with ; he has found it only once, in the rain 

 water of a muddy ditch. The preceding were taken from rather pure but 

 stagnant water. 



The second section {Mesostomata) comprehends the following species -. — 

 Derostoma grossum, {Planaria grossa, Miiller,) D. viridatum, {PL viridata, 

 Muller,) I), rostratum, {PI. rostrata, Muller,) and J), fusifurme, a new 

 species. 



In a great number of these species, M. Duges has recognized genital 



