142 THE MECHANICAL FUNCTIONS. 



The parts of the Spougia panicefi, which are 

 naturally transparent, contain at certain seasons a 

 multitude of opaque yellow spots, visible to the 

 naked eye, and which, when examined by means 

 of a microscope, are found to consist of groups of 

 ova, or more properly gemtnules* since we cannot 

 discover that they are furnished with any envelope. 

 In the course of a few months these gemmules 

 enlarge in size, each assuming an oval or pear-like 

 shape, and are then seen projecting from the sides 

 of the internal canals of the parent, to which they 

 adhere by their narrow extremities. In process of 

 time, they become detached, one after the other, 

 and are swept along by the currents of fluid, which 

 are rapidly passing out of the larger orifices. Fig. 

 55 represents one of these gemmules detached from 

 the parent sponge. When thus set at liberty, they 

 do not sink by their gravity to the bottom of the 

 water, as would have happened had they been 

 devoid of life; but they continue to swim, by their 

 own spontaneous motions, for two or three days after 

 their separation from the parent. In their pro- 

 arrange themselves in linear juxtaposition, as if by a kind of organic 

 crystallization, therel)y forming the stems and branched filaments 

 of these apparent plants. These singular productions, which have 

 been recently studied by M. Gaillon, and which he has established 

 into a natural family, denominated Nemazoaria, seem, in their 

 progressive developements, to possess alternately the characters of 

 vegetables and of animals, and may perhaps be regarded as con- 

 necting links between the two great kingdoms of living nature. 

 (See " Appercu d'Histoire Naturelle, et Observations sur les limites 

 qui separent le Regne Vegetal du Regne Animal. Par B. Gaillon. 

 Boulogne, 1833.") 



* Gemmule is a term derived from the Latin word gemma, a bud; 

 and its meaning, as applied to zoophytes, is that of a young animal, 

 not contained within an envelope, or egg. 



