ON SOME PLYMOUTH HOLOTHURIANS. 



215 



tubes are arranged to the right and left of the mesentery supporting the 

 alimentary canal in a position which is just behind the middle of the 

 length of the animal. In this species the tubes join up at their attached 

 ends to form a very short duct which unites almost immediately with its 

 fellow on the opposite side to form the main gonoduct. The number 

 of tubes on each side of the mesentery was noticed in all the specimens 

 and recorded in columns 4 and 5 in Table 2 (see p. 215). It was found 

 that the same number of tubes occurs only rarely oji each side of the 

 mesentery, but that there is generally about the same number : on the 

 whole, however, more were found on the left than on the right side. 



Table 2. — Illustrating the variation in the distribution and number of 

 gonadial tubes in Cucumaria saxicola of different sizes. 



Eggs in various .stages of development were observed in the tubes of all the females. 

 R. means a rudimentary; sm. a rather small tube. 



