444 CHARLES RUSSELL BARDEEN 



entiated in the form of a rudimentary S shaped tube which may 

 contain no continuous lumen. The pericardial cavit}' is not 

 infrequently' abnormally dilated. Rudiments of some of the 

 larger vessels in the head and trunk may usually be distinguished 

 in the more advanced specimens but these rudiments frequently 

 seem to be discontinuous. Since no artificially injected speci- 

 mens have been studied it is impossible to decide definitely to 

 what extent the vascular system is differentiated in discontinuous 

 parts in these specimens. In the liver, capillaries may be dis- 

 tinguished in the better developed specimens, but elsewhere in the 

 body they are usuallj^ difficult to trace, owing in part to the 

 anaemic condition of most of the specimens. In some specimens 

 no blood corpuscles can be found in the blood vessels. In 

 most specimens they are far fewer in number than in normal tad- 

 poles of a corresponding stage. 



Lymphatic system. Abnormally dilated 'lymph' spaces are 

 very frequent in the more advanced abnormal larvae but beyond 

 this little concerning the development of the lymphatic system 

 can be learned from a study of the specimens. 



Gentio-urinary system. It is only in the more advanced larvsB 

 that much can be made out concerning the genito-urinary organs. 

 In these specimens the pronephric tubules are generally abnormal 

 in form and considerably dilated. The Wolffian ducts may not 

 extend to the cloaca. Frequently they are abnormally dilated. 

 Mesonephric tubules are seldom differentiated in specimens 

 which show marked abnormalities during the latter part of larval 

 differentiation. The sex cells in some specimens appeared reduced 

 in numbers but the data on this point are inconclusive. 



Muscular system. The myotomes are sometimes well differ- 

 entiated in places even in specimens in which there are profound 

 abnormalities in other organ systems. On the other hand, they 

 may sometimes be distinguished with difficulty in larvae in which 

 these abnormalities are less profound. Sometimes the myotomes 

 are represented by scattered muscle cells. In specimens in which 

 there is a unilateral defect in the spinal cord there is usually an 

 absence of myotomes in the region of the defect. In the head 

 in the more advanced abnormal larvse the musculature is usually 



