188 LINEUS SANGUINEUS. 



are often placed on dark, muddy and highly odoriferous sand or gravel, and the water cannot be 

 otherwise than brackish at the estuary of a river. 



The skin of this species gives an acid reaction. 



The ova are deposited in gelatinous sheaths from January to May, and abound under stones 

 in pools and moist places between tide-marks. 



The want of precision in the descriptions of authors has burdened the literature of the 

 present group of animals with diverse synonyms, especially as regards this widely distributed 

 species. Though 0. F. Miiller's specific name rubra has the priority, and fusca comes next in 

 order, yet, as each of these terms implies something at variance with the true description of the 

 species, as contrasted with others, or retains some elements of doubt, I have chosen the suc- 

 ceeding title, viz. gesserensis (of the same author), as more appropriate. His description of the 

 form under the latter name, and the accompanying figure, leave no room for uncertainty, even the 

 pale specks for the exit of the reproductive elements being noticed on the sides. Miiller's 

 Ascaris rubra was probably a small specimen of the same worm. Tor some time I was inclined 

 to include Planar ia viridis under the present species, but the thick or almost baccate appear- 

 ance of some of the figures in the * Zoologica Danica' gives rise to so much doubt that I have not 

 deemed it prudent to unite them. The Planaria carnea of Jens Rathke (' Skrivter af Naturhist. 

 Selskabet,' &c, 5 te Bd., p. 83, tab. iii, f. 10, a, b) appears to be referable to this common 

 form. It is doubtful whether the Lineus oculatus of Montagu (MS.) applies to L. gesserensis or 

 to L. sanguineus. Dr. Johnston first described the species as having two eyes, but, as OErsted 

 states, the author had only seen a young specimen. He afterwards gave it four eyes, but the 

 number of the latter is of little moment, since the animals are so liable to vary in this respect. 

 Dr. Johnston also observed the presence of the gregariniform parasites for the first time, though 

 he did not correctly interpret their nature. The Nemertes obscura of E. Desor, from the coast 

 of the United States, is allied in the closest manner to this species, and the Nemertes flaccida of 

 M. van Beneden is either a pale variety of the same or L. sanguineus. 



3. Lineus sanguineus, Jens Bathke. Plate V, fig. 2. 



Specific character. — Eyes more regularly arranged than in the foregoing ; snout narrower. 

 Body more elongated, and of a reddish or reddish-brown hue. Regenerates easily. 



Synonyms. 



1799. Planaria sanguinea, Jens Rathke. Skrivter af Naturhist. Selsk., vol. v, i, p. 83. 



1828. „ unicolor, Johnston. Zool. Jour., vol. iii, p. 488 (?) 



1829. „ octoculata, Ibid. Op. cit., vol. iv, p. 56. 



1837. Nemertes (Borlasia) octoculata, Ibid. Mag. Zool. and Bot., vol. i, p. 537, pi. 18, f. 2. 



„ „ „ (Ersted. Kroyer's Naturhist. Tids., iv, p. 579, in nota. 



„ Planaria sanguinea, Ibid. Op. cit., pp. 572 and 579, in nota. 



1844. Nemertes octoculata, Ibid. Entw. Plattw., p. 91. 



„ „ sanguinea, Ibid. Op. cit., p. 92. 



1846. Borlasia octoculata, Johnston. Ann. Nat. Hist., vol. xvi, p. 434. 



