298 THE DEVELOPMENT OF THE NYMPH. 



their appearance whilst the muscles and other tissues of the 

 larva undergo disintegration. The change is preceded and 

 accompanied by a great increase in the number of blood 

 corpuscles, and the whole contents of the pupa, except the 

 rudiments from which the imago is developed, assume the 

 form of a white cream-like fluid, or pseudo-yelk, the cellular 

 elements of which, granule cells, are similar to the cellular 

 elements of the great food-yelk of Birds and Reptiles. 



As my own observations confirm those of Kowalevski in 

 almost every detail, I shall give the results of his investigations. 

 He says : 



' If we investigate the changes which are going on in the 

 young pupa by sections, it will be seen that the muscles and 

 other tissues are completely surrounded by the blood plasma, 

 and that, more especially in the anterior part of the body, vast 

 numbers of blood corpuscles, leucocytes, adhere to the 

 muscles. Pupae one or two hours old already exhibit indica- 

 tions of the penetration of the sarcolemma by these corpuscles. 

 Generally some of the muscle fibres exhibit one or two leuco- 

 cytes in their interior close to the sarcolemma, whilst others 

 still remain without any. A few hours later many corpuscles 

 are seen within the muscle fibres. Minute cracks then appear 

 radiating from these cells, and processes of the cells or the cells 

 themselves may be seen lying in these cracks. Soon afterwards 

 minute fragments of the muscle substance are seen entirely 

 imbedded in these leucocytes, which are thus converted into 

 the well-known granule cells. There is never any difficulty in 

 distinguishing the nuclei of the leucocytes from those of the 

 muscle, as they are smaller and more spherical. New cells are 

 now seen continually passing into the cracks, and the latter 

 extend so that the muscle becomes more and more broken up. 

 When the whole muscle is permeated by the leucocytes, these 

 assume a spherical form and separate from each other. The 

 sarcolemma has by this time disappeared ; it is probably so 

 perforated by the passage of leucocytes that it allows the fibre 

 to fall to pieces. The muscle nuclei, which Viallanes believed 

 to proliferate, are removed in the same way as the rest of the 



