418 RICHARD EVANS. 



larva described in the early part of this paper as type D are 

 briefly as follows : 



(1) The flagellated cells pass in at a rate which is but slightly 

 different for the upper and lower surfaces. 



(2) There is a stage^ however brief, during which the pupa 

 consists only of plasraodial aggregations inside and flattened 

 epithelium outside. During this stage there are no signs either 

 of the larval cavity or of incipient canals. The former has 

 been obliterated, while the latter have not as yet made their 

 appearance. 



(3) The flagellated chambers are derived for the most part, 

 if not entirely, from the flagellated cells of the larva. 



(4) The canal system only appears after the plasmodial 

 aggregations break up and form the flagellated chambers. 



(c) Further Remarks on the Formation of the General 

 Canal System. 



In specimens derived from the larvae of type D all the canals 

 and spaces must be formed anew, for the larval cavity is entirely 

 obliterated, and there are no lacunar spaces or canals such as 

 were found in the pupse derived from type C. The canals appear 

 as spaces in the interior soon after the flagellated cells have 

 begun to emancipate themselves from the plasmodial aggre- 

 gations, and have passed into the syncytial condition described 

 above. It is needless to say that the canals at their first appear- 

 ance do not possess a proper lining in the form of flattened inde- 

 pendent cells. Later on, however, they become lined with 

 cells possessing granular nuclei, which are derived from two 

 sources. In the region of the subdermal cavity they are derived 

 to a great extent from the cells with granular nuclei which had 

 been already produced at the time of metamorphosis. In the 

 interior, on the other hand, they are produced as in the larva by 

 the gradual conversion of the cells with vesicular nuclei, as can 

 be seen from the presence of small central corpuscles in many 

 of these cells. 



Owing to the continued formation of the cells with granular 

 nuclei from those with vesicular nuclei, many of the former 



