CONTRIBUTIONS TO THE ANATOMY OF THE HIRUDINEA. 487 



constituted walls passes through the rounded cells e — c and then 

 emerging at h, perforates a single series of cells Ji — /, and passes 

 down to the external aperture /. The section a b shows the 

 condition of one of the rounded cells which thus has its own 

 lumen receiving ductules and is perforated in two places by 

 cells each with its own special lumen. This gives the cell a 

 most remarkable histological character. 



The lumen of the nephridiumin Clepsine might be actually 

 dissected out, as is represented diagrammatically in woodcut, 

 fig. 8, c. There is the funnel a. Upon this follows a portion 

 b — c, with a very slightly branched lumen and then a portion, 

 c — e, with a rather more branched lumen, but from e to the 

 external aperture the duct is perfectly simple, always perforating 

 single cells, and without branches. 



Gnathobdellidae. Hirudo. 



The funnel in Hirudo has hitherto entirely escaped observa- 

 tion and its existence was denied by myself, by Schultze, and 

 by all previous observers. 



I have already fully described its position — it lies in a special 

 blood sinus, surrounded by red blood. This is the perinephros- 

 tomial sinus (fig. 61, pn. s. ; woodcut, fig. 4), and in those 

 segments containing testes (7 — 16) lies upon the dorsal wall of 

 the testis. In the two segments, 17 and 18, which contain 

 nephridia posterior to the testicular region, the funnels exist 

 in similar sinuses, while in the five nephridial bearing segments 

 (2 — 6) anterior to the testicular region the funnels do not 

 exist. The funnel lies at the end of the " testis lobe." This 

 testis lobe ends in a mass of cells of a spongy nature (fig. 49, 

 6.), the ductules being very irregularly arranged. The arrange- 

 ment and the character of the funnel about to be described 

 seem to me to be explicable by a theory of degeneration fol- 

 lowing upon a loss of function. Attached to the extremity of 

 the " testis lobe " is a large mass covered with cells, which 

 generally present upon their free surface a somewhat bilobed 

 appearance due to a depression upon the surface ; such cells 

 have the shape shown in fig. 50, b, others of these cells are 



