154 ZOOPHYTES. 



and the other bearing some relation to the mass or bond of union. Some- 

 thing is contributed for each separate portion, and something for the 

 whole. 



Farther, when the mass is composed of animals combined in groups, 

 the functions to be discharged become still more complex, as pertaining to 

 the common mass, to the group, and to the individuals whereof the group 

 is constituted. 



It is with certain products of this description that we are to be now 

 briefly engaged, and those in particular denominated the Compound As- 

 cidice. 



The history of the whole is yet involved in much obscurity. Great 

 difficulty is experienced in determining the different species, arising, per- 

 haps, from the irregular form, and varied aspect, under which the same 

 species is often presented — owing, no doubt, in cases innumerable, to 

 vigour, to age, and position. Thus I can do little more than offer a 

 few very general observations on what has fallen within my notice regard- 

 ing such a wonderful example of organic combination. 



Botryttus verrucosus. — The Warty Sea-Fig. — I am compelled to as- 

 sign a provisional name to this product, from inability to recognise its 

 identity with any of the species enumerated by authors. But from the 

 description and peculiarities here given, others can easily restore it to its 

 proper place, should I be mistaken. 



The BotryUus verrucosus, or Warty Sea-Fig, which, by an oversight, 

 I had on a former occasion specified as an Aplidium, occurs occasionally 

 in our Scotish seas, but under such different forms, that I hesitate on in- 

 cluding those that follow within the same section. 



It may be described generally as a subgelatinous product, composed 

 of an indefinite number of ascidian animals, arranged in systems or groups, 

 with a common central cavity to each system. These groups invest in- 

 organic substances, either as a superficial stratum, or they constitute fleshy 

 or subgelatinous masses, generally pendent from the marine Algae. 



All are of a semi-transparent appearance, of greenish, greyish-brown, 

 or yellow colour. 



