Anatomical structure of Aspidogaster conchicola. 511 



being considerably different — that of the right side as passing back- 

 wards and giving off" irregularly lateral branches , while that of the 

 left side divides primarily into two large stems of which the one turns 

 to the foot and the other to the posterior end. Many of my first 

 attempts seemed to indicate also great irregularity and the impossibility 

 of reducing such a complex system to a definite arrangement. The 

 apparent binary division of the left main stem, when it occurs, is to 

 be found in the delay with which the two posteriorly directed branches 

 separate from each other. The anteriorly directed branch, which turns 

 at a sharp angle, has come by the further growth of the animal to 

 be separated a little distance from the other two. With this slight 

 correction the main branchings of the left may be brought into harmony 

 with those of the right side. Fig. 15 shows the system of the right 

 side as seen in a compressed living animal. The only imperfection 

 I find in it, so far as it goes, is the absence of the first odd branch 

 to the anterior sucker which I was unable to find in this specimen. 

 A few branches are followed out to the end organs. With this as a 

 skeleton one can fill in mentally the rest of the branches with their 

 funnel organs and get a fair conception of the semi-excretory system. 

 This right half can be divided into an anteriorly running stem, a 

 posteriorly running stem along the vitellarium, and a middle stem 

 turning downwards and which at the second division gives three 

 branches extending respectively forwards, downwards and backwards. 

 Following the middle one, it again soon divides in three which may 

 be held to have a similar distribution. The middle one of these runs 

 in the neighborhood of the testis. The backwardly projected stem 

 soon breaks up into three of which its middle member gives origin 

 to three secondary capillaries and each of the latter produces three 

 primary capillaries each of which is terminated by a funnel. Again 

 and again I have followed different courses and find, as to number 

 and method, the same holds. Even the odd twig forming the first 

 branch into the neck undergoes the same process and trifurcates five 

 times after leaving the main trunk. 



If all the branchings are regular and the process is repeated six 

 times, we can, by a simple calculation, estimate the number of funnel 

 organs in a single Aspidogaster. Thus: 4X3X3X3X3X'^ 

 will give the number for one side and doubling this we get a total 

 of 1044 — a very respectable number to be distributed in an animal 

 of 2V2 cubic millimeters contents. 



In such a case we should be able to find these organs in con- 



