ROTIFERA: NEMERTEA. 635 



Rotifera inhabit both fresh and salt water and damp moss. Some are 

 parasitic, either externally, as Seison on Nebalia, or internally, as species 

 of Albertia in the coelome of Lumbricus and the intestine of Slugs (Lima- 

 cidae]. They are said to resist the effect of drying. The Philodinadae 

 certainly can do so, as they surround themselves with a gelatinous layer. 

 The affinities of the class are doubtful, but certain resemblances to the 

 Chaetopodan Trochosphere are to be traced. 



Hudson and Gosse, 'The Rotifera,' London, 1886. 



Die Rotatorien der Umgegend von Giessen, Eckstein, Z. W. Z. xxxix. 1883. 

 Beitrage zur Naturgeschichte der Rotatorien, Plate, J. Z. xix. 1886 (with literature 

 quoted). An attempt to re-classify the Rotifers, Hudson, Q. J. M. xxiv. I884 1 . 



Pedalion, Hudson, Q. J. M. xii. 1872. Trochosphaera, Semper, Z. W. Z. xxii. 

 1872. Rotifer vulgaris, Zacharias, Z. W. Z. xli. 1884; A. N. H. (5), xv. 1885. 

 Asplanchna, Hudson, Journ. R. Micr. Soc. (2), iii. 1883. Melicertidae, Joliet, A. Z. 

 Expt. (2), i. 1883. 



Chitinous parts of mastax, Gosse, Ph. Tr. 146, 1856. 



Nephridia, Plate, op. cit. pp. 56-7, 76-7, 98-100. 



Power of resisting drought, Gavarret, A. Sc. N. (4), xi. 1859; Davis, Slack, and 

 Hudson, Monthly Microscopical Journal, xi. 1873 ; and winter habits, Cubitt, 

 op. id. v. 1871. 



Egg formation and development, Tessin, Z. W. Z. xliv. (i and 2), 1886. 



CLASS NEMERTEA. 



(Nemertini : Turbellaria Rkynckocoela.} 



Unisegmental Vermes, with a ciliated ectoderm ; a pair of cephalic 

 ciliated pits or grooves ; a protrusible proboscis, placed dorsally to the oeso- 

 phagus, opening above the fiiouth, and surrounded by nervous cerebral com- 

 missures. Two main nervous cords extend from the cerebral ganglia, one on 

 either side, to the posterior end of the body, and are sometimes united by a 

 supra-anal commissure. There is a coelomic blood-vascular system. A pair of 

 nephridia is situated in the anterior or oesophageal region. The generative 

 organs are simple and paired, and extend in a series down either side of the 

 body. The sexes are as a rule separate. Development takes place with or 

 without metamorphosis. Mostly marine. 



The body is frequently brilliantly coloured. It is usually elongated, 



1 Plate has recently proposed to divide the class into two groups, the Aductifera ( = Philodinadae) 

 and the Ductifera. In the former there are two ovaries but no oviducts. The trochal apparatus 

 retains the primitive form of two rings, one behind the other ; the posterior styles are 4-6 in number, 

 and the four cement glands open on their apices ; the nervous system has no lateral antennae, &c. 

 The Ductifera have a single ovary (germarium and vitellarium) and an oviduct; the trochal 

 apparatus is modified ; the terminal styles are never more than two ; there are one or two dorsal and 

 two lateral antennae, &c. See Z. W. Z. xliii. 1886, p. 233. 



