464 LEPTONEREIS GLAUCA. 
sections, of two segments each ; these by three sections, of three segments each; and then 
by four or five sections, of four segments each. Behind these, sections of three segments 
reappear and are continued to the pygidium. 
Experiments showed that the rate of regeneration of the different sections varied accord- 
ing to the region of the body from which they came, being most rapid in those from the 
middle region. 
Regeneration of anterior segments appears to continue, until the original segments come 
to occupy exactly the same position in the regenerated worm as they had occupied im the 
parent, and then stops. Posterior regeneration was more active when the original segments 
came from the anterior end of the parent worm. The posterior portion of a female stolon 
regenerated a complete souche of thirteen segments, and had commenced to regenerate a 
stolon-head when it was found (Allen). 
In connection with the Syllids, the recent interesting remarks of MM. Caullery and 
Mesnil! on viviparity and parthenogenesis may be mentioned. They found a form, Hhlersia 
neprotoca,? N.S., amongst Lithothamnion at La Hague, with young at different stages of 
development to the number of a dozen in the ccelom, and without traces of any male, or 
of hermaphroditism. They are inclined to suppose that in certain forms of these and other 
Syllids a life-cycle occurs, in which, after normal reproduction, parthenogenesis takes place, 
as in Aphides and Cecidomya, in some generations. 
Pierantoni’® has also extended the list of species of Pionosyllis bearing ova or larve. 
His P. gestans has a series of fourteen to fifteen well-developed larvee along the ventral 
surface ; P. elegans bears eleven or twelve laterally ; P. papillosa carries a large ovum on 
each side for twenty-one segments, whilst P. minuta has fewer ovigerous segments. The 
dull purplish ova of Spherosyllis hystrix, again, are borne below the dorsal cirri. 
A considerable number of Syllids (over a dozen) have been added to the British Fauna 
lately, and more will probably yet be found by a further minute search of shore and sea. 
Hamity NEREIDA. 
Genus LEPTONEREIS, Kinberg, char. emend. 
Proboscis with only soft papille; dorsal and ventral divisions of the foot distinctly 
divided. In the male heteronereid the body is divided into three regions, the middle only 
being modified for swimming, the posterior region having peculiar fused bristles.* 
LEPTONEREIS GLAUCA, Claparede, 1870. Plate CX VI, fig. 9—head and anterior region. 
Specific Characters—Head short, about the depth of the buccal segment, posterior 
border entire ; anterior eyes large, elliptical; posterior smaller, rounded; tentacles and 
| “Compt. rend., t. clxi, p. 576, 1916. 
* mies, YOUN’, Ty 05, ViViparous. 
3“ Arch. Zool. Napoh,’ vol. 1, pp. 231—252, taf. x and xi, 1911. 
* Ramsay, ‘Journ. M. B. A.” 1914. Vide vol. 1, part i, p. 263, for further information. 
