I 



IV FAT-BODY 1 3 7 



body which thus maintains, as it were, an independent feeble life, 

 subject to the demands of the higher parts of the organisation. 

 It undoubtedly is very important in metamorphosis, indeed it 

 is possible that one of the advantages of the larval state may be 

 found in the fact that it facilitates, by means of the fat-body, 

 the storage in the organisation of large quantities of material 

 in a comparatively short period of time. 



A considerable quantity of fat tissue is found in the peri- 

 cardial sinus, where it is frequently of somewhat peculiar form, and 

 is spoken of as pericardial cells, or pericardial tissue. Some large 

 cells, frequently of pale yellow colour, and containing no fat, are 

 called oenocytes by Wielowiejski. They are connected with the 

 general fat-body, but are not entirely mingled with it ; several 

 kinds have been already distinguished, and they are , probably 

 generally present. The phagocytes, or leucocytes, the cells that 

 institute the process of histolysis in the metamorphosis of 

 Muscidae, are a form of blood cell ; though these cells are 

 amoeboid some writers derive them from the fat-body. The 

 cells in the blood have no doubt generally an intimate re- 

 lation with the fat-body, but very little accurate information has 

 been obtained as to these important physiological points, though 

 Graber has inaugurated their study. ^ 



Organs of Sex. 



The continuation of the species is effected in Insects by means 

 of two sexes, each endowed with special reproductive organs. It 

 has been stated that there are three sexes in some Insects male, 

 female, and neuter ; but this is not correct, as the so-called 

 neuters are truly sexed individuals, generally females, though, 

 as a rule, they are not occupied with the direct physiological 

 processes for continuing the species. 



The offspring is usually produced in the shape of eggs, which 

 are formed in ovaries. These organs consist of egg-tubes, a cluster 

 of which is placed on each side of the body, and is suspended, 

 according to Leydig^ and others, to the tissue connected wdth 

 the heart by means of the thread-like terminations of the tubes. 

 The number of egg-tubes varies greatly in different Insects ; 

 there may be only one to each ovary {Camjpodea), but usually the 

 ^ Biol. CentralU. xi. 1891, p. ,212. ^ ^g^^_ ^^^ German, xxxiii. 1867, No. 2. 



