PLANARIAN WORMS. 
399 
Schmidt has also in PI. cornuta described what he says 
may be spinarets, like those of a spider, but he doubts about 
them. I think it important to mention that Daly ell, in his 
“ Power of the Creator,” notices two or three species of Plana- 
rians as apparently spinning and hanging by threads. 
And now, before ending, I may urge those who can, to study 
and draw carefully any Planarians they may find, as material 
is greatly needed for % a complete history of Fresh-water Plan arise. 
The ponds on Hampstead Heath and the wonderful old pond at 
the Surrey Hardens (St. Thomas’s Hospital) I have found to be 
excellent hunting grounds. 
Bibliography. 
Duges (for habits and rough drawings of species). Ann. Sc. Natur. tome 
15, tome 21. 
Schmidt, Osc. (for descriptions and figures of genera of fresh- water Rhab- 
docoels). Die rhabdocoelen Strudelwurmer . Jena, 1848. Wien. Akad. 
Proc. bd. xxiii.— (For anatomy of Dendrocoels). Siebold und Kol- 
liker’s Zeitschr., bd. x. bd. xi. 
Schultze. Zur Naturgesch. der Turbellarien. Greifswald. 1851. 
Quatrefages (Marine Planarians and Nemertians). Ann. Sc. Nat. tom. 21, 
3rd ser. 
Claparede (Marine larvae, &c.). Geneva Academy. 1863. 
Mecznikow. Wiegmann’s Archiv (1865), and Ann. Nat. Hist. (1866). 
DESCRIPTION OF PLATE XIX. 
Diagram of the anterior half of a Nemertian worm : pr , proboscis ; 
p, preganglionic region ; c, ciliated cleft ; y, nerve ganglion ; 
m, ventrally-placed mouth ; gn, generative gland ; i, intestinal 
canal. Five times the natural size. 
Pilidium gyrans : a , rudiment of young Nemertid. Greatly 
magnified. 
Style-apparatus of the proboscis of a Nemertian. 
Anterior part of a Cercaria (from the Lymnceus stagnalis ), to show 
the striped integument. The mouth m, and the stylet s, placed 
in the prseoral or prae ganglionic region. 
Opistomum pallidum , Schmidt (copied from Schultze) : g, nerve 
ganglion ; o, mouth ; ph, pharynx ; tt, testes ; df, vasa deferentia ; 
vs, seminal vesicle ; pe , penis j G, genital opening ; va, vagina ; 
rs, receptacle of semen ; or, ovary j vi, yelk gland •, ut, uterus, 
with two eggs. 
Prostomum lineare , Ehr. (after Schultze) : pr, proboscis ; g, nerve 
ganglion ; m, mouth ; ph, pharynx ; t, testes ; vi, yelk gland ; 
vs, vesicle for semen ; pe, penis (with a hard dart) ; rs, recep- 
tacle of semen; ov, ovary; x, uterus (according to Meczni- 
kow) ; n n, water- vessels and their openings. 
Fig. 1. 
6 . 
