Pulyzoa of the Adriatic. 263 



margins thin, a little turned inwards, at the top on each side 

 a short spinous projection. Avicula)'iiim placed a very short 

 distance below the top, rather small, (as seen from above) very 

 slender, elongate, straightish, miming out to a fine point in 

 front, the free extremity of the beak very short and slightly 

 bent. Ooecium terminal, very wide (wider than the top of 

 the cell), shallow, almost semicircular, raarginate round the 

 base, the front wall composed of slight membranaceous 

 material. 



B. sinq^hx belongs to the same section of the genus as B. 

 flabellata. The ovicell is extremely shallow, the basal poi*- 

 tion slightly hollowed out and surrounded by a rim-like 

 margin, and with a filmy membranous covering closing in the 

 upper part of the front. It seems to be intermediate between 

 the normal ooecium and the very rudimentary form which we 

 have in Bugula yliunosa form aperta. The zoarium, in tlie 

 only specimen examined, is about half an inch in height ; the 

 branches which divide dichotomously and are somewhat flabel- 

 late originate together at the top of a short stem and form a 

 cup-shaped growth. 



DiACHORIS, Busk. 



Diachoris hirtissima^ Heller, form cylindrical n. 

 Dr. Pieper's collection contains several specimens of an 

 exceedingly interesting variety of this species. Two forms of 

 the zoarium are known in this genus : one in which the cells 

 are more or less decumbent and repent, not indeed adnate to 

 the surface over which they spread, but attached to it by 

 means of tubular fibres and adhesive disks ; and another in 

 which they are united so as to constitute erect, bilaminate 

 fronds. To these must now be added a third, in which the 

 zooecia are aggregated, so as to form erect, cylindrical^ branch- 

 ing ste7ns of considerable height, rooted by a mass of tubular 

 fibres. These fibres, in the variety of the present species to 

 which I have given the name cylindrica, pass upwards, erect 

 and free, carrying lines of the interconnected cells in such a 

 manner as to form cylindrical stems. The fibres occupy the 

 hollow of the cylinder, and the cells, which lie closely toge- 

 ther in line, constitute the walls. The shoots are somewliat 

 loosely compacted and of lax habit, and towards the base the 

 cylinder is sometimes imperfect. Tliey grow in dense clusters 

 and are much branched dichotomously, attaining a height of 

 about two inches. The transformation which the species has 

 undergone in this variety is really remarkable. It is a Vincu- 

 laria amongst the BicellariidaB, and may teach us the true 



