THE P ARAB LAS TIC TISSUES. 



vs 



fat bodies, nor are the true cytogenic cells connected with 

 them, as they are according to Schaffer [131] in the larvae of 

 Lepidoptera. 



The multinuclear cell chaplets, which occur in both the larva 

 and imago, are closely related to the fat bodies. Those of the 

 imago at least appear to be young fat bodies, and the oinocytes 

 of the imago are probably fat cells, the fat granules of which 

 have been absorbed for the nutrition of the great food-yelks 

 (eggs) in the mature female. 



Recently the origin of the fat bodies in Insects has attracted 

 considerable attention, owing to its import in relation to the 

 parablast theory. C. Schaffer has, I think, satisfactorily traced 

 the development of the larval fat bodies in the Blow-fly to the 

 peritoneal coat of the tracheal vessels, but both he and Graber 

 also trace them in various insects to the hypodermic layer of 

 the integument. I think, however, the figures given by these 

 authors indicate that they had not to do with young fat bodies, 

 but with tangental sections of the hypodermis. Both authors 

 regard the cellular layer of the tracheae as also of hypo- 

 dermic origin, and as due to invagination, a view which I 

 regard as untenable (see Tracheal System). 



The Fat Cells of the Imago differ from those of the larva (p. 86) 

 in being frequently multinucleate. Biitschli [126, p. 558, 

 PL XXVII., Fig. 43], Claus,* and Bolles Leet concur in deriv- 

 ing them from multinucleate cell-chaplets similar to that 

 described by Weismann in the larva ; and my own researches 

 lead me to the same conclusion, except that the great cell- 

 chaplet of the larva certainly undergoes histolysis in the pupa, 

 although other and similar chains of multinucleate cells appear 

 in the young imago, and ultimately become fat bodies. 



The fat cells of the imago are loaded with fat granules, and 

 appear very similar to those of the larva, except that they 

 are smaller. These cells usually exhibit a single vesicular 

 nucleus. 



In the immature state they are mixed with smaller cells, 



* 'Zeitsch. f. vv. Zool.,' Bd. xxv., p. 266, PI. XIV. 

 t 'Recueil Zool. Suisse.,' torn, ii., p. 391. 



