FUNCTION OF THE (ENOCYTES OF INSECTS. 221 



exactly the same manner as the small amounts of hog extract 

 had been treated, and the immediate reaction was very char- 

 acteristic. Eighteen experiments of this sort were performed 

 and as all cells have catalytic ferments, other cells as the fat 

 cells, intestinal cells, etc., were submitted to the same tests. 

 When very small amounts of the extract from these cells (i. e., 

 amounts proportional to those of cenocyte extract) were used, 

 it was impossible to determine whether a pink color had developed 

 or not. 



CONCLUSION. 



I conclude from the preceding experiments that the cenocytes, 

 which have been regarded by previous investigators as glands, 

 secrete oxidizing enzymes. I do not know whether this is their 

 only function, but it is certainly one of them. At any rate they 

 do not secrete a fat-splitting enzyme. Since these cells, hanging 

 loosely to the tracheae, lie free in the blood, the enzymes which 

 they secrete may activate the oxygen of the body towards 

 combustion. That the cells actually secrete is indicated by the 

 fact that numerous observers, myself included, have detected 

 microscopical exudations around the periphery of the cyto- 

 plasm, especially at times when the nucleus is greatly ramified, 

 and therefore manifesting its great activity. 



Exactly what relation the cenocytes bear to the tracheae, I am 

 unable to say. I saw no definite attachment, but am inclined to 

 believe that a relation exists and that through this the oxydases, 

 one branch of the group of oxidizing enzymes, are able to get 

 their molecular oxygen with the formation of peroxides. It must, 

 moreover, be remembered that Wheeler, in 1892, found the ceno- 

 cytes of phryganeid larvae to be provided with delicate processes 

 which are attached to the tracheal hypodermis. That may, of 

 course, be simply a means for attachment and have nothing to 

 do with the passage of oxygen from one to the other. The loca- 

 tion of the cenocytes may be purely due to the absence of certain 

 mechanical forces. Wheeler found that "the cenocytes originate 

 by delamination or immigration from the ectoderm, just caudad 

 to the tracheal involutions and after their differentiation from 

 the primitive ectoderm never divide, but gradually increase in 

 size." Since they never divide after differentiation, the me- 



