98 EDWARD THELPS ALLIS, JUN. 



the arrangement in the anterior portion of the line^ that is^ 

 in the anterior portion of that part of the line that is called 

 by Garman the prenasal. Following this anterior portion^ 

 and extending to the hind end of the short median section, 

 there were groups of two or three tubules between each two 

 successive organs. Posterior to this median section the 

 tubules were less regularly arranged in reference to the 

 organs, and often had no apparent regular relation whatever 

 to them. The tubules vary greatly in length in different 

 parts of the line, being particularly long along the orbito- 

 nasal section of Garmau's descriptions, and immediately 

 ventral and dorsal to the spiracle. Opposite the spiracle 

 they are aborted or wholly wanting. Along the orbito-nasal 

 section of canal the tubules branch repeatedly, and open on 

 the outer surface by numerous pores, as shown in fig. 7. 

 The long tubules ventral and dorsal to the spiracle, on the 

 contrary, branch bat little, each branch usually having but 

 a single pore at its outer end. 



The first or most distal organ of the infra-orbital canal 

 lies near its anterior end, the canal there connecting with 

 the supra-orbital canal between organs 34 and 35 of that 

 line. The 24th organ of the line lies at the point where 

 the canals of opposite sides meet and anastomose in the 

 middle line. Beyond organ 29 the two canals separate again. 

 There are thus 2o organs anterior to the median section of 

 the canal, and 6 organs in that section. These 6 organs 

 lie on the dorsal or latero-dorsal wall of the canal, always 

 lateral to the median line, and opposite, or nearly opposite, 

 an organ belonging to the line of the opposite side of the head. 

 Between each successive pair of these organs there was a 

 single tubule on each side, that is, a pair of tubules, excepting 

 only between organs 26 and 27. The point between these 

 two latter organs is, morphologically, the middle point of the 

 median section of the canal, and there were here two tubules 

 on each side and a single median tubule. This was the only 

 median tubule found in the entire lateral system, but there 

 was, perhaps, such a tubule at the middle point of the supra- 



