320 HARMOTHOE IMBRIOATA. 



phorescence appears to be less vivid during severe weather and when confined for a night 

 or two in shallow vessels — a feature probably due to nervous prostration, or it may be 

 associated with approaching maturity. Specimens placed in a weak solution of picric 

 acid in sea water are not luminous, and the scales are not at first thrown off. 



Parasites. — The crustacean parasite Herpyllobius arcticus* Stp. Ltk. (Silenium 

 Polynoes, Kr.), occasionally occurs in arctic examples attached to the dorsum. Levinsen 

 also found another crustacean parasite, viz, Selio'ides Bolbroei, Lev., on one from 

 Greenland. 2 



On the dorsum, under the scales of a specimen from the tidal region at Balta 

 Sound, Shetland, numerous examples of a fine Loxosoma in various stages of growth are 

 found. 



A peculiar warty growth appears on the tentacular cirrus of an example from the 

 Gulf of St. Lawrence, and a series of minute whitish tubercles in an arctic example from 

 Bessels Bay. 



The bristles harbour many parasitic algae, besides mnd, foraminifera, and sponge- 

 spicules. At St. Andrews a small Sabella, Syllis, and Pholoe have been found amongst 

 the bristles, and young mussels occasionally fix themselves to the dorsal bristles. 



A translucent Ascaris, fully half an inch in length, occurred in the peri-pharyngeal 

 space of a female. The slightly truncated snout showed one or two blunt papillae, while 

 the pointed posterior end had a few acute papilla. Though outside the gut it had free 

 access to the perivisceral fluid, and, moreover, the long anterior casca passed forward on 

 each side of the space. 



Development. — The broad outlines of the development of this species have been 

 known for a considerable time, and it may therefore form the type for the group. 

 Comparatively small species are occasionally found mature, or carrying ova under the 

 scales. 



Michael Sars, 3 as early as 1845, described the occurrence of ripe examples of 

 Harmothoe in February and March. He noticed the mature females exhibited a change 

 of colour, becoming pale rose behind the anterior fourth. This was due to the eggs 

 which covered the dorsum. He thought that the ova passed out by a small aperture 

 above the feet. He watched the development of the egg from early segmentation to the 

 movement of the embryo by cilia, and its slightly greenish coloration. The larvas 

 (monotrochous trochophores) escape after two weeks, swim freely, and bear two eyes, 

 with a pre-oral band of cilia. Max Miiller, Desor, and others have also described the 

 development. Desor, however, fell into the error of supposing that the larva escaped 

 from a similar ciliated investment to that of Linens obscurus. 



Max Miiller, 4 in the young of either this or an allied form, pointed out that new 

 segments' were interpolated posteriorly. He described the dimorphism of the bristles, 



1 'Kgi. Danske vidensk. Selsk. Skrifter naturv.-mathem. afd./ Bd. v, 1861; and Kroyer, 

 < Naturh. Zidskr./ 3 die E., Bd. ii, 1863, &c. 



2 < Yidenskah. Med. fra den nat., &c./ i Kiobenh., 1887. 



3 " Zur Entwicklung der Anneliden," ' Arch. f. Naturges./ 11 Jahrg., v. 1, 1845 ; and ' Ann. Nat. 

 Hist./ 1845, p. 188 (vol. xvi). 



4 "Ueb. d. Entwicklung u. Metamorph. d. Polynoen," ' Mull. Archiv/ Jahrg. 1851. 



