294 CAUSES OF DEGENERATIVE EVOLUTION 



W. Burck has called attention to, without 

 endeavouring to explain, other instances of the 

 persistence of functionless organs. A large 

 number of Anonacese bear flowers which do not 

 open, and which are self-fertilizing (cleistogamous 

 flowers). None the less, they have retained the 

 corolla, the original purpose of which was to 

 attract insects. 1 



Burck has called our attention to the circum- 

 stance that several species belonging to the same 

 genus produce cleistogamous flowers, and that it is 

 improbable that this condition has been acquired 

 independently by these species. One would thus 

 have to admit that the original type must be very 

 remote, as it has given rise to descendants of 

 specific distinction, and yet the useless corolla has 

 persisted through the long series. 



Parallel examples may be found among animals. 



MacTiaerites is an insect which inhabits caves 

 in North America. The females are quite blind ; 

 the males, on the other hand, have preserved, or 

 seem to have preserved, well- developed eyes ; but 

 are these eyes real? An abyssal fish, Ipnops? 

 seems as if it had enormous eyes extending from 

 the corner of the snout some distance along the 

 neck, but these organs are not really eyes ; they 



1 "W. Burck, Ueber Kleistogamie im weiteren Sinne und das 

 Knight- Darwinsche Gesetz (Ann. Jard. Bot. Euitenzorg, viii., p. 

 122, 1889). 



2 Dollo, La Vie au sein des mers, p. 242, Paris, Bailliere, 1891. 



