344 



ANIMAL STUDIES 



life, the withdrawal from the crowd of animals and from 

 the struggle which it necessitates. The young tunicate is 



FIG. 207. The pigeon horn-tail (Tremex 

 columba), with strong boring ovipositor. 



FIG. 2Q8.Thalessa lunator boring. After 



COMSTOCK. 



FIG. 209. The large ichneumon fly 

 Thalessa, with long flexible oviposi- 

 tor. The various parts of this ovi- 

 positor are spread apart in the fig- 

 ure ; naturally they lie together to 

 form a single piercing organ. 



a free-swimming, active, tad- 

 pole-like or fish-like creature, 



which possesses organs very like those of the adult of the 

 simplest fishes or fish-like forms. That is, the sea-squirt 



