28 . HISTORY OF THE SUBJECT. 



A valuable paper on the embryology of Nemertes was produced by E. Desor in 1850, 1 

 which for the first time disclosed the remarkable development in certain of the Anopla. His 

 observations were made on a species, from the shores of New England, allied in the closest manner 

 to the common British Lineus gesserensis. The ova are laid in the form of flask-shaped capsules, 

 each of which contains from one to seven yolks. Desor discovered that after a time the yolk 

 becomes ciliated, and that the young Lineus emerges from this ciliated investment, so that just 

 before extrusion there are two spheres of ciliation, viz. the external coating, and the skin of the 

 contained embryo. 



Dr. Joseph Leidy 2 described in 1850-51 a species of Rhynchoscolex {B. simplex), which 

 is probably a Nemertean, and a new genus, Emea, constructed for the reception of a 

 freshwater species from the neighbourhood of Philadelphia. He calls the proboscis the 

 alimentary tract, and the stylet-region a gizzard armed with a dental apparatus. In the former, 

 he states, are numerous villose appendages (evidently referring to the glandular papillae of the 

 proboscis). He recognised the proboscidian fluid and its corpuscles, but he defined it only as 

 occupying the interior of the body. His statement that the generative system consists of two 

 tortuous and capacious tubes is also open to doubt. 



In a second paper in the same volume 3 he mentions MecJcelia lactea, n. s., a form which 

 can swim like an eel. This is evidently one of the Anopla, yet he terms the mouth the generative 

 aperture. 



In a third communication 4 he makes some amendments in the description of his genus JEmea y 

 apparently after having seen the memoirs of De Quatrefages. He now observes that the (Esophagus 

 is styliferous, being " furnished at its bottom with a single spine or nail-like tooth, and four others 

 on each side in a rudimentary condition, enclosed in a sac." He likewise says that the intestine 

 becomes obliterated posteriorly, whereas he formerly stated that the mouth and anus were 

 terminal. 



In a paper remarkable only for the unsoundness of the views contained therein, Mr. Charles 

 Girarcl, in 1851, proposed to class the Nemerteans and Planarians with the Mollusca, and not 

 with the Annelids at all. 5 It is scarcely necessary to enter into his theories, but it may be inte- 

 resting to note that this reformer rests his conclusions on so many grounds (with special reference 

 to the Nemerteans) as the following : — Their soft, glutinous, ciliated body ; their simple nervous 

 system, consisting of a small number of cephalic ganglia ; their eye-specks, development and habits. 



Dr. Max S. Schultze published an important work during the same year on the Turhettaria 

 of Ehrenberg, accompanied by exquisitely engraved copper plates. 6 The Nemerteans, however, 

 were but briefly alluded to in the third part of the treatise, under the heads of Prorhynchus 

 stagnalis and Tetrastemma obscurum respectively. The former is chiefly interesting on account 

 of the atrophied condition of the proboscis and its stylet-apparatus, which the author considered 

 to be an aggressive organ, poison being instilled into wounds by the contraction of the posterior 

 chamber. It forms an advantageous comparison with the aberrant Nemertes carcinop/iila. 



1 "Boston Journ. Nat. Hist./ vol. vi, No. 1, pp. 1 — 12, pis. 1 and 2. 



3 ' Proceed. Acad. Nat. Sc. Philadelph./ vol. v, p. 125. 



3 Ibid., pp. 223 and 224. 



4 Ibid., pp. 287 and 288. 



5 c American Journ. Sc./ 2nd ser., vol. xi, No. 31, pp. 41 — 53. 



6 c Beitrage zur Naturgeschichte der Turbellarien.' Erste Abtheilung. 7 pis. Greifswald, 1851. 



