227 



His remarks had reference principally to this function as per- 

 formed in very small insects, such as the very minute Miles or 

 Acaridce, living on the feathers of birds. The question would 

 very naturally present itself, whether in such small animals the 

 spermatozoa are proportionally small, and therefore proportion- 

 ally numerous, or whether they are large and few. It is found 

 that the size of these particles does not materially change with 

 the size of the animal ; that they are as large in the smallest 

 lizard as in the largest alligator. It is therefore evident, that in 

 the AcaridcB their number must be very small. Dr. Burnett had 

 succeeded in counting them in some species, and found them to 

 be from twenty down to ten, and even fewer in number. In the 

 female he found the number of ova to correspond with that of the 

 spermatozoa, leading to the inference that an ovum requires but a 

 single spermatozoon for impregnation ; a fact demonstrated by 

 Newport by experiment in the case of Batrachians, but in the 

 present instance by nature herself. The economy of reproduc- 

 tion is made as certain and effectual in this case as possible, by 

 means of a prolonged act of copulation, the male being attached 

 to the female by a pair of strong anal hooks. In the animal 

 kingdom generally, the number of individuals of any given 

 species is in proportion to their size. Now the number of the 

 Acaridse is incalculable. It would therefore seem that the pro- 

 creative capacity of a species is not necessarily, as is usually 

 supposed, in a direct but rather in an inverse ratio to its num- 

 bers. These facts tend to sustain the opinion of the plural origin 

 of these insects. 



Dr. Burnett referred to the observations which he had made, 

 the results of which he had laid before the Society two years 

 since, (See Proceedings, Vol, III. p. 262,) on some of the pro- 

 creative peculiarities of the common Humble Bee, {Bombus 

 Americanus ;) namely, that the males die after impregnating the 

 females in the autumn, while the females, after hibernating 

 through the winter, bring forth three broods, the first of neuters, 

 the second of females, and the third of males. Heretofore, 

 these facts have been quite anomalous in this class of animals ; 

 but during the past two years, Dr. Burnett had noticed the same 

 succession of events in the economy of other insects, namely, 

 the BuprestidcB. These are the enemies so destructive to the 



