426 Recent Literature. [Jaly, 
“ Finally, it also happens that parts or organs of the larva, during the 
period of the post-embryonal development, will pass into the correspond- 
ing parts of the imago without any change, or with very little change. 
Thus, for instance, a part of the adipose body of the larvæ.of the Mus- 
cide and of the ant pass into the adipose cells of the imago. It is 
worthy of notice that itis only after the last molt of the larva of Core- 
thra that those large bundles of colossal adipose cells make their ap- 
pearance, which surround the anterior tracheal bladders; but they pass 
without any change into the imago, without furnishing, directly or in- 
directly, any material for the formation of the organs of the imago. 
This fact, taken singly, does not weigh in favor of the importance of 
the adipose body as a living, plastic material for building up the organs 
of the imago in the period of the post-embryonal development. The 
so-called histolytic processes, in the sense of Weismann,! as well as the 
process of an independent formation of the cells from the products of 
the destruction of the larval organs, I have never observed. 
“ The comparative examination of all these processes, which take place 
new formation and destruction, as well as from their morphological 
meaning, the highest place in the series of all the insects must be 
granted to the Muscide. Besides the already known facts of compara- 
tive anatomy, may be adduced the data obtained through embryolog- 
ical researches, which confirm the above-mentioned statement. The 
position of the imaginal discs in the cavity of the body, the mode of 
development of the head, the chest, the proboscis with all its parts, the 
entire destruction of the exoderm of the first four segments of the larva, 
the entire destruction of all its abdominal muscles, etc., — all these cir- 
_ cumstances lead to the conclusion that the organism of the Muscide has 
undergone more modification than that of any other insect, during its 
phylogenetic development. The mode of development of the strata or 
rudiments in the imaginal discs of the Muscidæ, as compared to that in 
the discs of other insects, serves to confirm that conclusion. In the 
larve of Muscide, both strata of rudiments of the disc are formed anew 
from a common cellulose germ on the peritoneal envelope of the tracheal 
tube, or on the neurilemma of the nerve. In Corethra, Miastor, and in 
the Hymenoptera, strictly speaking, the mesoderm of the disc is alone a 
new formation, developed with the participation of the nerve and the 
tracheal tube; the exoderm of the disc is derived from the epithelial 
1 I say in the sense of Weismann because later observers, as C. Chun, P. Mayer, 
esses are called by them histolyse. Weismann, on the contrary, clearly distinguishes 
this second histolytic process from the three other processes of formation of the 
gans of the imago. The histolyse, according to Weismann, takes pl l 
_ the organ of the larva furnishes the skeleton to the organ of the imago, etc., etc. 
