50 ELIOT R. CLARK 



containing, for the most part, lumina, but without circulation. 

 Extending peripherally from them are several blind-ending pro- 

 jections. As regards the rate of circulation, through branch 6 it 

 is relatively 'fast,' while through branch 10 it is 'slow.' To sum- 

 marize the condition of the vessels for the small area selected, 

 there is a simple irregular plexus of capillaries with wide and 

 rather irregular lumen, some of them with and some without 

 circulation. For convenience, the principal afferent and effefent 

 capillaries have been called arteriole, or arterial capillary, and 

 venule, or venous capillary, though they are of capillary size and 

 appearance. 



In figure 2 (a day later) a 'slow' circulation has started in a 

 numlDer of vessels which had been non-circulating on the previ- 

 ous day, and several new sprouts and connections between 

 sprouts have formed. In figure 3 this has continued, and has 

 been accompanied by an increase in the rate of circulation in 

 some of the vessels. On the other hand, there are some vessels 

 in which the circulation has diminished, or ceased altogether. 

 In figures 4 and 5 the same processes have continued — a slight 

 formation of new vessels, with modification of the rates of circu- 

 lation in many of the vessels, an increase in some and a decrease 

 in others, in addition a new change has become marked, 

 namely, the disappearance of certain capillaries, in which the 

 circulation had ceased, or in which the circulation had never 

 started. 



Owing to the fact that the prolonged use of chloretone had 

 caused a slowing of growth processes, the larva was allowed to 

 develop in fresh water, with observations at less frequent inter- 

 vals, in order to see the fate of the vessels being watched, after a 

 considerable amount of growth had taken place. A record was 

 made on April 22, which showed very little change from the 

 record of April 20. The succeeding records were made May 12, 

 May 20 and May 31. "While these later records are not close 

 enough together to show all the growth changes, they show very 

 well the new capillary areas which have developed, their relation 

 to the vessels already present, and the changes which the earlier 

 formed vessels have undergone, in consequence. Thus it will be 



