ON BUDDING IN ANIMALS. 3 



be no question as to whether increase can be most advan- 

 tageously carried out by the one method or the other, and this 

 has to be borne in mind in considering Weismann's remark,* 

 that in the lower animals, " whenever increase apart from the 

 ordinary method became advantageous, it was more readily and 

 better supplied by fission and budding." Moreover, as in these 

 minute animals there is no distinction of the sexes, nature is 

 deprived of one of the means she is stated to employ to produce 

 variation (Brooks and Weismann). Further, no clear differ- 

 entiation into elements destined to build up the body (somatic) 

 and those associated with the continuance of the species (though 

 the nucleus has long been connected with the latter) exists, and 

 thus the process of budding is simplified. Lastly, it is difficult 

 to trace any relationship, in such forms, between the budding 

 and special adaptation due to demands made by the conditions 

 of life. 



In the great division of the Metazoa budding in one form or 

 another especially characterizes the lower types. Thus buds 

 are common amongst the Sponges, and various species can be 

 multiplied by cutting off pieces and planting them on suitable 

 sites. The bath-sponge of the Levant (Turkey-sponge), for 

 instance, has been successfully propagated in this manner. 

 Complex branching is likewise prevalent in the group, and the 

 two features just mentioned probably weighed with the illustrious 

 Ehrenberg in tenaciously asserting that Sponges were vegetables. 

 The so-called gemmules, again, found in such species as the 

 fresh-water Sponge (Sjjongilla) are modifications of buds. As 

 eggs of the ordinary kind occur in these animals, and are in 

 many forms the chief method of spreading them in the waters 

 around, a choice between the two modes of increase is now 

 possible, each being adapted, as in the fresh-water Sponge, for 

 its special season. The formation of gemmules, that is, little 

 masses of sponge-tissue, in addition to the ordinary method of 

 increase, probably was slowly acquired, first by the separation 

 of the little masses of sponge-tissue, then the formation of a 

 capsule, and, lastly, by the modification of the remarkable 

 spicules characteristic of the latter. Sponges which formed 

 buds of this kind might be supposed to have a better chance of 



* II., p. 216. 



B 2 



