242 M. MIYAJTMA : 



They number in all 9G and are arranged approximately in a 

 single row, which, being interrupted at the lower edge of the disc, 

 assumes the form of a horse-shoe. (Woodcut 2, P). At the two 

 ends of the horse-shoe are situated the smallest gonosomes which 

 stand at a distance of 15 mm, across from each other. The 

 length of the stalk of the gonosomes varies from 20 mm. to GO mm. 

 While the gonosomes nearer tlie lower edge of the disc are on 

 the whole shorter than those nearer the upper edge, it is to be 

 noticed that the larger and smaller gonosomes are placed alter- 

 nately, indicating faintly the two circles in their arrangement, 

 the larger gonosomes being placed in the outer, and the smaller 

 in the inner, circle. 



The region of the disc outside the gonosomes is marked with 

 numerous radial canals (Woodcut 2, R.) w^iich run from the 

 base of the gonosomes to the margin of the disc. This region 

 thus assumes the form of a wide horse-shoe, whose two arms 

 gradually diminish in their breadth towards the lower edge of 

 the disc until they terminate at that edge. Hence this region 

 varies in breadth, measuring 20 mm. on the median line at the 

 higher edge, and 35 mm. on the lateral region, while on the lower 

 side both arms are practically zero. 



The radial canals (PI. XV, Fig. 1, r.c.) slightly swell out the 

 surface of the disc thus giving the latter an undulating appear- 

 ance. The canals are intercalated by solid cords (PI. XV, Fig. 1, 

 i.e.) which appear on the surface of the disc as opaque lines. The 

 canals and the intercalated cords are longest in the lateral region 

 where they run obliquely across the disc, and are longer than 

 the breadth of this region. The canals situated nearer the lower 

 edge are smaller and shorter than those higher up, until at the 

 both arm-ends they are practically nil. On the other hand the 



