3O8 E. H. STRICKLAND. 



signs of worm parasites. As a gnu-nil rule, however, ilu- largest 

 larva? were found to contain one or more worms coiled up within 

 the abdomen. One would naturally expect this rule not to 

 be YITV constant, if, as conjectured, it is simply due to a more 

 >luv;:J-!i u-mprrainent and increased appetite on the part of the 

 parasitized larva?. 



A case of a Mermis parasitizing ants was described by Professor 

 \Yheeler ('07) and here also he noticed a great increase in size 

 of the host due to a greatly increased appetite during the larval 



A number of tin- worms were dissected out and sent to Professor 

 T. ]]. Montgomery who pronounced them to belong to an 

 undetermined species of Mermis. 



RETARDATION OF DEVELOPMENT OF THE HISTOBLASTS DUE TO 



MERMIS. 



On making a closer examination of the parasitized larvae a 

 far more remarkable effect than that of increased size was noticed, 

 for it was found that the presence of Mermis parasites, no matter 

 in what numbers, has a direct effect on the development of the 

 histoblasts. In a normal larva of about 10-10.5 nim. which is 

 the maximum length, and is attained immediately prior to the 

 blackening of the respiratory filament histoblasts, the latter are 

 quite large and owing to their white color readily visible to the 

 naked eye; especially when the larva has been killed in Kahle's 

 or Gilson's fluid (Plate II., Fig. 6). If a parasitized larva of 

 the same, or greater, size be examined no trace of the histoblasts 

 can be discovered with the naked eye, and can only be detected 

 with difficulty under a dissecting lens. Under the low power 

 of a compound microscope, however, they are seen to be repre- 

 sented by small white traces of the organs which should at this 

 time be far advanced in development (Plate II., Fig. 7). A 

 do-i- examination fails to reveal any differentiation of these 

 in led histoblasts into the component parts of the adult, 

 or pupal, organ. 



The parasitized larva rarely develops beyond this stage, though 

 I have observed specimens which were turning reddish brown, 

 and contracting slightly as a healthy larva would, shortly before 



