EVIDENCE FROM COLONIAL OR COMPOUND ANIMALS. 281 



the sides of canal locks and in similar situations, illustrates the former 

 method of development. This species propagates its kind by verit- 

 able buds, whilst it also produces eggs ; and another curious fact, 

 possessing a significant bearing on the individuality of the sponges, 

 consists in the observation that when two Spongillse are placed in 

 contact they merge together into one. They may also be divided 

 artificially, or may separate spontaneously into two or more organisms, 

 each of which will lead an independent existence. The sponges, 

 then, may be hereafter referred to as a group of animals which, 

 whilst originating from eggs, as do higher beings, yet retain much 



d 



FIG. 189. ZOOPHYTES, b and d, magnified portions of a and c respectively. 



of that tendency to segregation and separation into distinct and 

 elementary parts which we may reasonably maintain is probably a 

 primitive and fundamental character of all living beings. 



Nearly allied to the sponges are the little freshwater polypes named 

 Hydra (Fig. 188), and the marine plant-like organisms familiarly 

 known as "Zoophytes" (Fig. 189). Here we at once enter the 

 domain of animal " colonies/' and find intensified and illustrated in 

 the plainest fashion those tendencies towards division and segregation 

 of body which, at the best, are but dimly marked in lower organisms. 

 The hydra, existing as a little green tubular body attached by one 

 extremity to a water weed, and exhibiting at the free end a mouth 

 and tentacles at certain seasons exhibits a growth of small projec- 

 tions on its sides. As these projections increase in size, they grow into 

 the likeness of young hydrae (Fig. 188), each developing a mouth and 

 tentacles, and possessing, so long as they adhere to the parent body, 

 free communication with the interior of the latter. These budded 

 hydrae may in their turn produce buds, and a veritable genealogical 



