486 WARO NAKAHARA 



problem of the internal metamorphosis of insects. The best 

 work that has been done upon the subject, however, seems tome 

 to be that of Perez's ('02), dealing with the postembryonic de- 

 velopment of Formica rufa. Since this is a very valuable paper 

 on account of its accuracy and thoroughness, and since the works 

 of other writers are more or less fragmentary, or not satisfactory 

 in some other ways, it has seemed advisable to take up the 

 French work to review for all. 



In this paper the author has definitely established that the adi- 

 pose cells are the seats of progressive accumulation of fatty and 

 albuminous reserves during the larval life of insects. In the 

 larva just hatched he observed that the adipose cells are small, 

 12 to 15 micra in diameter, and spherical, each with a single 

 spherical or ellipsoidal nucleus which contains a small amount 

 of chromatin granules. The cytoplasm is of two layers, peri- 

 nuclear and peripheral, and shows a number of vacuoles, with- 

 in which osmic acid preparations show blackened fat droplets. 



The cells become greatly enlarged in the larvae of 2.5 mm., 

 attaining 30 to 40 micra in diameter. Binucleate cells are fre- 

 quently observed at this stage, and although Perez was rather 

 inchned to think that this condition is due to the amitotic divi- 

 sion of the nucleus, he did not draw any conclusion, considering 

 the fact that Berlese claimed the occurrence of mitosis in the cells 

 in a certain case. It is also at this stage that the eosinophile gran- 

 ules begin to appear in the cell-body in addition to fat droplets. 

 These granules are spherical, 3 to 5 micra in diameter and very re- 

 fractile. From all the available evidence, Perez interpreted them 

 as representing albuminous reserves in the cell. In 6 mm. larva 

 the enlargement of the cells is carried still further and many of 

 them are more than twice as large in diameter as those in the 

 stage just examined. These large cells are filled with albuminous 

 granules and fat droplets. The nuclei begin to be irregular in 

 shape and a few of them are ramified. The ramification of the 

 nucleus is carried to the extreme in the full-grown larva ready 

 to pupate. 



The series of changes, similar in the main to that noted by Perez 

 in Formica, has been observed by many other writers in various 



