8 THE ZOOLOGIST. 



by the addition of its remarkable type (Bipinnaria) to its de- 

 velopment. A pelagic larva developing directly — for aught that 

 we know— would apparently have been equally efficacious in 

 peopling the waters with its countless swarms. Yet it cannot 

 be denied that these peculiar larvae are characteristic of forms 

 which occur in enormous numbers in the sea, as, for instance, 

 the Sand-stars, Brittle-stars, and the common Cross-fishes. 



Amongst the Worms, budding is remarkably prevalent in 

 various groups. Even in the parasitic forms such as the Cestodes 

 it is exemplified in the scolices of Tcenia ccenurus forming Ccenurus 

 crebralis in the Sheep, the daughter-scolices, each with its armed 

 head, budding from the interior of the parent-cyst. Another 

 example is the well-known Tcenia echinococcus forming hydatids 

 in man by the development in the liver and lungs of numerous 

 daughter-vesicles, even to two generations. The advantages of 

 budding in perpetuating the species are sufficiently illustrated in 

 the former case. Thus, if no bud were formed on the interior 

 of the cyst, the death of the Sheep would be that of the Ccenurus 

 also, but the presence of numerous buds suffices to spread them 

 broadcast amongst the Dogs that eat the head of the Sheep. 

 Thus the vicious circle is kept up, for the scolices become tape- 

 worms in the Dogs, and their eggs are by and by introduced with 

 food into the body of the living Sheep. 



The soft ciliated worms called Turbellarians show great 

 capacity for regenerating mutilated parts, while in some of the 

 elongated forms the fragments become perfect animals, as in the 

 Nemertean termed Lineus sanguineus, Jens Eathke, each fragment 

 of which develops a head with brain, sense-organs, and other 

 parts in a comparatively short time. Besides this power of 

 regeneration, certain forms present a similar condition to the 

 Echinoderms, in so far as the larval Nemertean is budded from 

 the Pilidium. As many of the Nemerteans are littoral and con- 

 fined to the bottom, such a method of increase would tend to 

 carry them to distant sites, since during the growth of the 

 Pilidium and thereafter during the development of the Nemertean 

 bud a considerable space may have been traversed. Yet such 

 forms would be exposed to the attacks of predatory crustaceans 

 and other animals even more than the young of types like Lineus 

 obscurus, which attain some size before leaving their protective 

 capsules. 



