AND THE LOWEE ANIMALS. 37 



inarily composed of sarcode, and gradually .assume 

 their special features afterwards ; ■ but when first 

 perceived they differ only in size from . the adult 

 forms. The embryo, in point of fact/ is a miniature 

 of the perfect being. In the course . of develop- 

 ment every animal exhibits very strange , phenomena, 

 both as to its entire economy, and in regard to 

 special organs ; " and ; this is particularly the' case 

 with reference to mammalia. r Daily, ay, even hourly, 

 the' scene "is changed, and this . unsettled , con- 

 dition applies not only - to essential, but- also to 

 merely accessory organs. One might fancy that 

 Nature was feeling her way to a conclusion. ■-, Here 

 may be seen cavities being gradually partitioned 

 off, divided, -. as it were, , into distinct chambers,- or 

 drawn out in a the form of canals, which, in their 

 turn, are often refilled with . solid matter and con- 

 verted into ligaments ; , in , another^ locality, we ; ob- 

 serve previously solid masses transformed : into cavi- 

 ties,', membranous- folds being rblled out into tubes, 

 isolated portions of tissue drawn together to form a 

 continuous organ, or even a mass hitherto entire, 

 being gradually cut up into several new structures. 

 Not only the form and proportions, but the relations 

 also of the various mechanisms are being momentarily 

 altered. Parts which at first' had been" closely related 

 separate from each other "and become distinct, and 

 organs which Had heretofore been, distant from each 

 other, form ties of close, alliance. Those apparatus 

 whose office is a temporary one rapidly increase in 

 size, acquire an enormous' volume, and eventually 

 disappear altogether. Others are, arrested in their 

 growth at a certain period, and though all the organs 



