47 



Vascular System— In L. variegatus a pair of transverse vessels 

 connects the dorsal and ventral vessels in each of several 

 anterior somites. They are situated just anterior to the septum. 

 They are small in somites back of XX, and are so close to the 

 wall of the intestine and so covered by chloragogue cells that 

 they are seldom recognizable. A single pair of cseciform, 

 contractile, branched vessels, connected only with the dorsal 

 vessel, is contained in the anterior part of each somite posterior 

 to XV (Ratzel, 1868), and, according to Dieffenbach (1886), 

 smaller ones are found as far forward as IX. The description 

 of the circulatory system of L. inconstans in my earlier treat- 

 ment of that species (1895) was very incomplete and did not 

 give enough data for comparisons, but as far as transverse 

 vessels are concerned the conditions existing in that species 

 and in L. variegatus are closely similar. In L. inconstans the 

 paired vessels which connect the dorsal and ventral vessels, 

 in the posterior part of each somite, are recognized with dif- 

 ficulty posterior to XVII, and the csecal branches of the dorsal 

 first appear in XI and then occur regularly, there being' one 

 pair, and only one, in each somite. In each of the two 

 species of Trichodrilus, in the middle region of the body there 

 are four or more csecal branches of the dorsal vessel on each 

 side in each somite, instead of a single one as in each species 

 of Lumbriculus. 



Sperm at hecce. — In L. variegatus there is much variability 

 in the position and arrangement of the spermathecae. Vejdovsky 

 reported three pairs in X — XII; Hesse found four pairs in 

 X — XIII; and Wenig found them more or less asymmetrically 

 distributed in IX— XV. In L. inconstans I have found five 

 pairs in XI— XV or in XII— XVI. In Trichodrilus but one or 

 two pairs are found, and these are in XI or in XI and XII. 

 The spermathecal pores of both species of Lumbriculus are at 

 least as high up on the sides as the ends of the transverse 

 diameter, while the pores of both species of Trichodrilus are 

 described as behind the ventral setae. 



