DESCRIPTIONS OF GENERA AND SPECIES. 187 



the Cestoda, Trematoda, Nematoda, Acanthocepliala, 

 Acarina; in sliort, for all creatures which undergo a 

 metamorphosis and change of hosts, otherwise for many 

 of these groups a revision of the nomenclature would 

 have to be commenced, which would give rise to a 

 confusion in the present nomenclature, the extent and 

 final result of which it is not possible to foresee." 



Unfortunately, in consequence of differences of 

 opinion upon other points, this report was not confirmed 

 by the fourth Congress ; but was referred back to the 

 Committee for further consideration, and no fifth 

 Congress has yet been held.* 



I am not aware of any other attempts to settle the 

 question except individual opinions. 



It appears to me therefore that all the existing 

 authorities are in favour of not adopting names in the 

 Acarina which are based upon immature forms ; and 

 this appears to me to be reasonable ; although I am 

 aware that many eminent naturalists hold an opposite 

 view. I cannot think it desirable that a name should 

 be adopted which is attached to a description and 

 figure which are utterly unlike the adult creature and 

 from which it could not possibly be recognised ; more- 

 over if the opposite rule were established, no amount 

 of care in searching before naming a new species 

 would ensure an author from having his name subse- 

 quently upset ; in addition to these arguments there is 

 the well-known objection of the large number of well- 

 established names which would be cancelled. 



The Tyroglyphidse seem to me to be an extreme 

 instance of the undesirability of adopting names 

 founded upon immature specimens and upon characters 

 which simply imply immaturity ; because in this family 

 such names are usually founded upon the Hypopus ; a 

 stage which is not only immature and entirely unlike 

 the adult, but is also adventitious, not occurring in the 



* Since writing the above the Berlin conference of 1901 has been 

 held ; at the time of going to press I do not know if it has dealt with 

 the subject. 



