STRUCTURE OF THE AMAROUCIUM TADPOLE 83 



a thickened ganglionic portion in the right lateral and ventral 

 walls of the sensory vesicle. 



The statolith-bearing cell projects for its entire diameter into 

 the cavitj" of the sensory vesicle, and is therefore a pendent 

 structure. In the living tadpole the statolith appears to be con- 

 tained in a cup-shaped depression at the distal end of the cell, 

 but sections show that it lies wholly within a vacuole-like cavity 

 of the statolith cell and is surrounded by a delicate layer of cyto- 

 plasm (figs. D, 5, and 6). The statolith is composed of a sub- 

 stance that is not disintegrated by strong acids and is not bleached 

 by chlorine. It is very hard and, when struck by the edge of 

 the section razor, is usually torn from its base and dragged through 

 the tissues. 



Tadpoles with two statolith cells are occasionally found, but 

 they are rare. 



The part of the sensory vesicle formed by the ganglionic por- 

 tion of the static organ is so located that it comes into contact, 

 at its most ventroposterior end, with the side of the visceral 

 ganglion, and nerve fibers probably pass from the former to 

 the latter at this point, but no 'acustic' nerve, such as has been 

 described by Salensky ('93) to connect the 'gehor organ' with 

 the visceral ganglion in the larva of Distaplia, is present in the 

 tadpole of Amaroucium. 



VISCERAL GANGLION 



The vertically situated part of the larval nervous system* 

 which connects the sensory vesicle with the nerve cord has been 

 called the visceral ganglion. A cortex made up of a single layer 

 of large nerve cells and a longitudinally striated medullary por- 

 tion may be distinguished in it, but no trace of a neural canal 

 can be found either in longitudinal or transverse sections (figs. 

 C, D, 3, and 10). 



From a point on the left side of the ganglion, located just below 

 the level of the hypophysial duct, a comparatively large bundle 

 of nerve fibers emerges as a nerve trunk and can be traced ob- 

 liquely upward and forward to the region above the endostyle a 

 short distance anterior to the oral siphon where it apparently 



