1877. ] Recent Literature. 425 
accompanied by the following processes : Processes of destruction, when 
organs or tissues of the larva are entirely or partially disintegrated. The 
products of this disintegration are not used immediately in the develop- 
ment of new histological elements, but are assimilated by suction and 
play the part of nutritive materials. Processes of transformation, I eall 
those morphological processes, during which the formation of a new 
organ takes place without the participation of a newly formed morpho- 
logical rudiment, but when the old organ, without being destroyed, 
passes into the a. corresponding organ of the imago, the 
newly appearing organ differing more or less, morphologically and his- 
tologically, from the old one. Thus the central nervous system of the 
larve of Muscide is not destroyed, but is transformed into the central 
nervous system of the imago, the latter differing very much, in its shape 
and structure, from the former: new parts have appeared ; the first knot 
of the abdominal cord, not existing in the larva, is differentiated; the 
ganglion opticum is newly formed; the shape and structure of the ab- 
dominal cord are changed, etc. The histological elements of the tissues 
of the new organ are derived from those of the transforming larval 
organ.- It is very probable that the dorsal vessel of the imago of Mus- 
cide is only transformed from the dorsal vessel of the larva. It seems 
to me that in the Museide the dorsal vessel does not interrupt its 
functions during the period of post-embryonal development: very often 
the contractions of the dorsal vessel of Anthomyia rufipes were observed 
during the second and third day after pupation, when the greater part of 
the larval organs were already destroyed. The trifling differences be- 
tween the dorsal vessel of the imago, as compared to that of the larva, 
May consist in its shape, the number, shape, and position of its wing- 
Shaped muscles, the number and position of the venose openings, etc. 
“ Processes of the formation of new organs. The variety of these proc- 
esses depends, of course, on the morphological and physiological con- 
ditions of the newly forming organ. These processes consist in the 
building up of an organ of the imago from a special morphological 
Pimat. Thus from the morphologioal aie called imaginal 
dises, are evolved entirely new parts of the body of the imago, 
with their different tissues — head, thorax ay he extremities, muscles, 
nerves, etc.; portions of the cephalic discs are converted into the com- 
pound eyes of the imago; out of the thickening of the abdominal seg- 
ments of the larva of Anthomyia is developed the musculature of the 
abdominal segments of the i imago, etc. It must, however, be at the same 
time remembered that there are no well-marked boundaries between 
~ these different processes; the terms used are intended merely to id 
nate the most marked phase of this or that process. The d ns 
given of those processes have only a relative meaning, like all our mee 
tions in morphological science. 
