THE EVIDENCE FROM DEGENERATION. 



361 



A 



the details of their structure, the "wheel animalcules" present 

 details equally interesting with their exhibition of " potential 

 vitality." The female animalcules possess a complete digestive 

 system, a set of water vessels, a nervous ganglion, and other be- 

 longings ; but their partners are decidedly inferior creatures, since 

 their digestive system becomes totally abortive ; 

 whilst in size, the males are likewise far excelled 

 by the lady rotifers. How this degeneration 

 and disappearance of digestive apparatus and 

 the inferiority of size have been produced in 

 the male rotifers, may be a matter regarding 

 which difference of opinion will certainly exist 

 in biological minds. The fact that retrogression 

 is here illustrated, however, 

 cannot be questioned. It 

 may also be added that, in 

 all probability, the extreme 

 development of the function 

 of perpetuating the species, 

 and the extraordinary fer- 

 tility of production wit- 

 nessed in these animalcules, 

 may satisfactorily account 

 for the abrogation of diges- 

 tion in favour of reproduc- 

 tion. Thus, to the other 

 causes of degeneration in 

 animal life and structure, 

 we may append that which 

 takes origin from the ex- 

 treme or excessive develop- 

 ment of one function over another. Physiological development' in 

 one direction, overstepping the natural and ordinary limits, runs 

 concurrently with destruction of life's equilibrium, and naturally 

 tends to produce degeneration and simplification of other organs 

 and of other duties of life. 



How far the theory of degeneration we have thus briefly discussed 

 may be applied in explanation of the peculiarities of animal structure, 

 remains as a task for the future of biology to satisfactorily determine. 

 Possibly the corrections which the future of every hypothesis carries 

 with it may be many and sweeping. The deductions and inferences 

 we extract from a study of degeneration to-day may perchance be 

 falsified by the higher and newer views of the to-morrow of biological 

 science. But enough has been said to show that, even in a cursory 

 review of the doctrine of degeneration and retrogression, many phases 



FlG. 259. ROTIFERA. 



