Anatomical structure of Aspidogaster conchicola. 513 



ovary and testis for the more terminal branches may be directed 

 away from these organs. 



The walls of the larger trunks from the ventral, collecting vessels 

 to the first tri-radiate division possess a fine circular musculature and 

 presumably also a longitudinal layer. In these the nuclei do not 

 bulge into the lumen, as in the ventral canals, but rather to the 

 outside. 



. At the points of division and occasionally between these points 

 may appear large bladder-like expansions of the vessels as if these 

 had been subjected to too great a pressure. On the walls of some 

 of these I have seen several different ciliary organs situated in such 

 a way as to indicate that the bladder had taken into it portions of 

 the bases of the branches. 



The ciliary organs are of three or more sizes corresponding with 

 the diameter of the vessels in which they are found. In the larger 

 vessels they are often situated on a little bend in the wall in such 

 a way as to throw their axes more nearly along the axis of the vessel. 

 Their distances apart vary. In the largest part of the main stem 

 with a diameter of 8 /< I found their bases il f^i apart and each 

 ciliary cone 20 f^i long. In this case the point of one overlapped the 

 base of the next anterior to it so that two or three seemed to make 

 one continuous long organ the wave passing uniformly from one onto 

 the other. By watching one of these apparently extremely long ciliary 

 organs for a time there would come a period when a slackening of 

 the motion would permit me to recognize its two or three constituent 

 members. P'arther back they were not so close. In large vessels are 

 sometimes two organs on opposite sides working together. Each is 

 composed of a number of cilia lying parallel, side by side. This can 

 be seen when the animal has been mounted for some time and has 

 begun to die. The cilia then can be observed in very slow motion 

 each for itself. In the fresh, vigorous worm the cilia of one group 

 are either fastened to one another side by side or they all act so 

 much in unison that because of their rapidity they seem to form one 

 piece of a long conical form. In the dying animal the cilia of an 

 organ appear frayed out — their free ends forming a broad front. That 

 this condition is not simply caused by the long and gradual death of 

 the animal may be seen from perfectly fresh specimens where the 

 ciliary organs of a portion of a vessel, either on account of too great 

 a pressure or because of exhaustion, will stop, apparently rest a short 

 time, and then start again. In this resting state the cilia are separated 



