EEOM THE EAST COAST OP SCOTLAND. 107 



This sponge was obtained by Dr. Bowerbank originally in a 

 sessile coating form on Tubidaria from Banif. The specimen for 

 which he established the species Isodictya gracilis came from 

 Lough Larne in Ireland, and is branched, with soft stem and 

 branches and minutely hispid surface, resembling exactly in these 

 points the present form. Judging, however, by the figures, its 

 skeleton-spicule is somewhat shorter and stouter, and its flesh- 

 spicule smaller than in I. JSdivardi ; so that its identity with that 

 species, which is asserted by Vosmaer (/. c), appears to me still 

 to require proof. At the same time it is interesting to find, as 

 we do in the case of the present specimens, an external identity 

 with the erect specimen from Ireland and an identity in minute 

 structure with the Scotch specimens. Some fragments, obtained 

 among the Hebj-ides, are described by Mr. Norman (Mon. Brit. 

 Spong. iv. p. 138) as " of massive form, and showing a tendency to 

 branch, measuring from half to three quarters of an inch long." 

 The present specimens difler somewhat from all these specimens : 

 they represent at least two individuals, now more or less broken. 

 The largest must have measured quite 100 millim. (4 inches) in 

 height when perfect; it branches subdichotomously and seldom. 

 The stem is narrow and subcylindrical, about 5 mm. by 3 mm. in 

 diameter; the branches also are somewhat flattened except at the 

 apices, where they measure about 2 mm. in diameter, whereas their 

 maximum diameter at about the middle of their course is about 

 7 mm. The smaller specimen is strictly cylindrical, and ranges in 

 diameter from 2 to 4 mm. The skeleton-spicules measure about 

 "23 by '008 mm. ; the flesh-spicules about "022 mm. in length. 



Sab. Stations 1 & 2 ; 40 and 42 fathoms. 



Distrib. ^siuS. {Bowerbank); Hebrides (iV^orwaw); 1-50 fathoms. 



SuBEEiTES Eicus, JoJinston {? ^sper). 



Halichondria ficus, Johnston, Brit. Spony. p. 144, pi. xv. fig. 4. 



Hymeniacidoa ficus, Bowerbank, Mon. Brit. Spong. ii. p. 206; iii. 

 pi. xxxvi. figs. 10-1/. 



Suberites ficus, Schmidt, Spong. Atl. Gebiet. p. 76. 



" Potato-sponge," F. Day, Notes on the Line and Herring Fisheries, 

 p. 18. 



Several specimens, most of which exhibit the interesting and 

 well-known commensalism of the Sponge with Pagurus, the 

 sponge growing on, and apparently causing the absorption of, 

 the shell, while the crab lives within it. 



Although it is stated by Bowerbank and Johnston that the 



