iS94-] 313 [Packard. 
allied to the Mycetophilidae, but after a careful reading- of 
Kraepelin's able memoir, and a reconsideration of the whole 
subject, I have for several years past been led to believe that 
they should be referred to an independent order, with closer 
affinities to the Diptera on the whole, however, than to any other 
order. 
It may be well to review briefly the history of opinion as to the 
position of the fleas in the class of insects, and which is taken in 
jiart from the memoirs of Dr. O. Tascheuberg and of Dr. Karl 
Kraepelin. The authors who jjlaced them among the Aptera 
were Linnaeus, Geoffroy, Cuvier and Diun^ril, and Gervais. 
Kircher referred them to the Ortho])tera. 
Those who regarded them as Diptera were IJoesel, Oken, 
Straus-Diirklieim, Burmeister, Haliday, Newman, Walker, von 
Siebold, with many German entomologists, and J. Wagner (188'J). 
They were regarded as Hemii)tera by Fabricius and by Illiger. 
The fleas were regarded as the types of a distinct order by 
DeGeer, Lamarck, Latreille, Kirby and Spence, MacLeay, 
Leach, Dug^s, Bouch^., van der Hoeven, Westwood, Landois, 
Brauer, and Taschenberg, besides Kraepelin. 
The fleas were placed by MacLeay and by Balbiani between 
the Diptera and Hemiptera ; by Leach between the Hemiptera 
and Lepidoptera ; by Dug^s between the Hymenoptera and 
Diptera ; and by Brauer they are given a position between the 
Diptera and Coleoptera. 
COMPAIIISON OF THE EmP,RYOXIC StAGES WITH THOSE OF THE 
Diptera. 
Thus far the studies made on the embryology of insects of 
different orders have elicited no characters of special taxonomic 
importance. The differential characters of the insect orders are 
largely adaptive, and were evidently evolved in postembi'yonic 
life. There seems to be much similarity between the embryos of 
the metamorphic orders, Coleoptera, Lepidoptera, Siphonai)tera, 
Diptera, and Hymeno;>tera. 
In his elaborate work on the embryology of the Diptera, 
Weismann^ describes and figures a single stage in the develop- 
iDie entwickliing- der diptereii. Zeit;<clir. fiir wi.ss. zool., 13, 180:). 
