breed: metamorphosis of the muscles of a beetle. 367 



forms has interpreted entirely correctly the phemomena which he has 

 seen. I affirm this the more confidently hecause in the controversy 

 which has arisen among these authors neither side has satisfactorily 

 explained the observations of the other. They all agree in describing 

 phenomena which are so like those of which I have here given an 

 account for Coleoptera, that it does not seem possible that there should 

 be any fundamental differences between the two groups. It is evident, 

 chiefly from the completed paper of Anglas (:01), that there is in 

 Hymenoptera a metamorphosis of most of the larval muscles, a degener- 

 ation of the remaining ones, and a new formation in the pupa of some 

 imaginal muscles. There are no persistent larval muscles such as exist 

 in Coleoptera, Lepidoptera, and orthorraphic Diptera, the abdominal 

 muscles undergoing a less complete metamorphosis than the metamor- 

 phosing muscles of the remainder of the body. 



The settlement of the whole controversy between the five authors 

 (Karawaiew, Terre, Anglas, Perez, Berlese) depends on the interpreta- 

 tion of the nature of certain cells found in the regions of the metamor- 

 phosing and degenerating muscles, these cells being apparently exactly 

 comparable to the cells in Coleoptera which have been spoken of in the 

 present paper as tracheal cells. N'one of the five authors mentioned 

 above has considered the possibility of the tracheal nature of these cells. 

 Nevertheless, none of their observations preclude such an origin. 

 Karawaiew, Terre, and Berlese contend that these cells are not leuco- 

 cytes, hut are developed from the nuclei of the larval muscles ; whereas 

 Anglas and Perez contend that they are not developed from the nuclei of 

 the larval muscles, but are leucocytes. Is it not possible that both sides 

 are correct in their negative conclusions and incorrect in their positive 

 affirmations 1 May not these cells be developed from the tracheoles of 

 the larval muscles, instead of from either of the tissues mentioned 1 

 None of these investigators has described the origin of the tracheae of 

 the imaginal muscles. Yet these tracheae are so exceedingly abundant 

 in the region of the wing muscles, that their origin cannot be so incon- 

 spicuous as to have been overlooked entirely, nor ought it to have been 

 neglected, as it has been. It is to be hoped that some of these authors 

 will at least consider the possibility of the explanation which I have 

 suggested, since, if correct, it will straighten out what otherwise is an 

 apparently hopeless controversy. 



We will now consider the researches on Coleoptera. A review of the 

 disagreements of Rengel ('96) and Deegener (:00) has already been 

 given in considering the changes of the intestinal musculature. It is 



