118 ANIMAL INDIVIDUALITY [CH. 



almost universally sets in first between the nutritive 

 and the reproductive functions the somatic and the 

 germinal. 



The Hydroids and their relations give us a series 

 closely parallel at first, though in a different grade 

 of individuality, with that of the Volvocidae, but 

 exceeding it considerably in length. Hydra, one of 

 the simplest hydroids known (Fig. 3, p. 39), has, like all 

 others, the power of budding ; but its buds eventually 

 become detached, so that it never forms more than 

 a very small and temporary colony. Besides this, 

 there is no division of labour among different polyps ; 

 all are alike, and whether they shall reproduce 

 sexually or asexually is dictated to them by the 

 external conditions. 



Then come the colonial forms : and all of these 

 show some division of labour. All, for instance, when 

 ripe, bud off special sexually-reproductive individuals 

 in the shape of little jelly-fish or medusae. Some- 

 times any polyp of the colony may be able to give 

 birth to one of these, but very often the ordinary 

 polyps reserve themselves for feeding, and special 

 mouthless polyps exist for the one purpose of budding 

 off the jelly-fish ; they are the producers of the 

 reproducers of the colony. It seems to be only later 

 that the somatic functions, the functions pertaining 

 to the single colony as opposed to the race, get 

 differentiated, as in Hydractinia (Fig. 10), where there 



