544 THK REPRODUCTIVE FUNCTIONS. 



repetition of those vegetative processes, liaving 

 similar objects in view, and the adoption of ana- 

 logous means for their accomplishment ; but so 

 widely different in character is the whole organic 

 economy of these two orders of beings, that we 

 perceive no resemblance in the mechanism em- 

 ployed for their formation. For the purposed of 

 animal life the nutrient juices must be brought into 

 active circulation by means of vessels extensively 

 pervading the system. Nature, then, hastens to 

 prepare this important hydraulic apparatus, with- 

 out which the work of construction could not 

 proceed. What may be the movements of the 

 transparent nutrient juices at the very earliest 

 period must, of course, remain unknown to us, since 

 we can only follow them by the eye after the nu- 

 tritive substance they contain has become consoli- 

 dated in the form of opaque globules. These glo- 

 bules are at first seen to meander through the mass, 

 unconfined by investing vessels; presently, how- 

 ever, a circular vessel is discovered, formed by the 

 foldings of the membrane of the embryo, along 

 which the fluids undulate backwards and forwards, 

 without any constancy.* A delicate network of 

 vessels is next formed in various parts of the area 

 of the circle, which are seen successively to join by 

 the formation of communicating branches, and ulti- 

 mately to compose larger trunks, so as to establish 

 a more general system of vascular organization. 

 But increased power for carrying on this extended 

 circulation will soon be wanted ; and for this pur- 

 pose there must be provided a central organ of pro- 



* These phenomena are similar to those which were noticed as 

 presented by the larvae of some insects and other inferior animals. 



