18 THE ZOOLOGIST. 



to expect increase by budding, since they approach in outline the 

 hydroid zoophytes. Loxosoma, again, bears a superficial resem- 

 blance to the solitary forms such as Hydra, and, like the latter, it 

 produces a few buds. The advantages of retaining a hold on a 

 suitable site and extending the polyparium into an arborescent 

 tuft, or a series of upright stalks, are in most cases obvious. 

 The budding in such as Cephalodiscus takes place with rapidity, 

 so that the new forms are soon ready to aid in the extension of 

 the general home (polyparium), which is the joint secretion of 

 the colony. The small number and large size of the eggs 

 evidently point to a peculiar larval stage, and are probably also 

 in relation with the feature just mentioned. 



In the simple Ascidians, increase by budding takes place in 

 the Clavelinidcs so as to form small colonies, in which each 

 ascidiozoid, according to Herdman, has a distinct test, but all 

 are connected by a common blood-system. The buds are formed 

 on a stolon — as vascular outgrowths of the three layers from the 

 posterior end of the body. 



The compound Ascidians, again, increase by budding, so as 

 to form colonies, in which the animals are buried in a common 

 investing mass, and have no separate tests. 



The Salpcs were formerly considered to be remarkable ex- 

 amples of budding, in which the aggregate forms were developed 

 from the solitary in the region of the endostyle near the heart ; 

 but Brooks has shown that the germinal mass is present in the 

 embryo of the solitary form, and extends into the stolon as the 

 latter grows out. It consists of investing epithelium and ova, 

 the latter forming a single row in the mature stolon, and in the 

 course of constriction to form the chain of buds (salpse) each 

 gets, as a rule, a single egg, with its epithelial coat, which is 

 differentiated into special organ (testis), follicle, and duct,* the 

 latter attaching the egg to the dorsal wall of the chain-salpa. 

 The solitary form thus does not arise from the chain-salpa, but 

 from an egg passed into the chain-salpa from the preceding 

 generation of the solitary form. 



No budding occurs in the Articulates (e. g. Crustacea, Myria- 

 poda, Arachnida, and Insecta), nor in the Mollusca or higher 

 forms. 



• ;: Through which fertilization takes place. 



