90 ALCYONELLA FLABELLUM. 



Iconography. — No published figure. 



Habitat. — Stagnant waters. Same as that oi A. fungosa. 

 Locality. — Chelmar Canal, Essex. G. J. A. 



The present -well-marked species I have great pleasure in dedicating to M. Van Beneden, 

 a naturalist who has not only done more than any one else in the particular department 

 to which this monograph is devoted, but who has enriched our knowledge of the lower 

 animals generally, by contributions numerous and valuable. 



A. Benedeni occurs in spongy masses attached to twigs, and other fixed bodies, and 

 resembling A. fungosa in their general appearance. They would seem, however, never to 

 attain to so large a size as the latter, the largest specimens I have seen, measuring about three 

 inches in length, and an inch in thickness at the thickest part. The tubes are closely adherent 

 to one another until within a short distance of their terminations, when they become free. The 

 ectocyst is dark brown, becoming rather abruptly lighter in the vicinity of the orifices, where 

 the peculiar characteristic fiirrow commences by a triangular notch-like space, and then passing 

 down as a narrow slit-like line, is finally lost where the adhesion of the tubes begins. When 

 withdrawn from the water, the tubes seem terminated by a little papilliform body, formed by 

 the endocyst, over which the ectocyst is continued as a very delicate, transparent, and colour- 

 less membrane. In extreme retraction, the papilliform terminations are entirely withdrawn 

 into the remainder of the tube. 



The statoblasts are of two kinds — free, and adherent. The free statoblasts are narrowly 

 elliptical, approaching to bean-shaped ; the disc is brown, minutely mamillated ; the annulus 

 is dull yellow, widely overlapping the disc, especially on the more convex side. These stato- 

 blasts are found in immense numbers towards the end of summer, lying quite free in the 

 interior of the tubes, and, on the rupture of the latter, escape, and instantly rise to the surface 

 of the water. Besides these bodies, others much less numerous are also found in the present 

 species, but are always attached to the inner walls of the tubes. They are broadly elliptical, 

 enclosed in a pergamentaceous shell, like the free statoblasts, but with a very narrow margin.* 

 Of their real import we are ignorant. 



I have met with A. Benedeni only in one locality, namely, the River Chelmar, in 

 Essex, where it existed in abundance, along with A. fungosa and the following species : 



3. Alcgonella flahellum, Van Beneden. PI. IV, figs. 1 — 4. 



Specific character. — Ccenoecium flabelliform, composed of branched prostrate tubes, fur- 

 nished with a furrow. Statoblasts broad. 



Synonyms. — 1848. Alcyonella flabeUum. Van Beneden, EechercLes sur Ics Bryozoaires fluv. de 

 Belg., p. 19 ; Mem. de I'Acad. Roy. de Belg., 1848. (Original figures.) 

 1850. Alcyonella flabcUum. Allman, Proc. Roy. Irisli Acad., vol. iv, p. 470. 



* Vide supra, p. 40. 



