On the generfttive Orirmis and Products of Tomopteris oni.sciforn1i^ K 443 



pairs of lateral appendages. This band of attachment gradually nar- 

 rows, till it is almost a tine thread, to the sides of the body. 



The oritice occupies a very definite position in relation to the 

 muscles. Gkeeff noticed and figured for T. eschschoUzia the muscles 

 to the lateral appendages, and my observations of T. onisciformis are 

 confirmatory. The ventral muscles for each appendage proceed from 

 the ventral muscles of the circular layer of the body-wall in two main 

 bundles. The band arising anteriorly, m. a., runs diagonally outwards 

 and is inserted on the posterior aspect of the lateral appendage of 

 the same segment, and crosses its fellow baud , m.p., which arises 

 posteriorly to be inserted on the anterior side of the inner wall of 

 the appendage. The genital orifice is placed in the inner angle formed 

 by these crossing bands, and, therefore, towards the middle line of 

 the body. The longitudinal muscles of the ventral surface, Fig. 36 m. I., 

 also cross the genital cleft laterally over its outer border, and medianly 

 also over a part of the orifice itself, acting as a kind of sphincter. 

 While the fibres of the longitudinal muscles maintain a straight course 

 on the outside of the opening, they are curved, outwards slightly, 

 and inwards very markedly, as represented in Fig. 36. In some, with 

 a wide open orifice, I have observed what appears to be a plug of 

 mucus filling up that portion which is not covered by the bending 

 fibres of the longitudinal muscular layer. 



While Leuckaut & Pagenstecher as well as Greeff saw two 

 pairs of openings, Quatrefages saw only one pair of female genital 

 orifices in front of the fourth pair of parapodia , but I can account 

 for this only on the supposition that his was an aberrant form. I 

 met with a similar female, which had one pair of openings in the 

 fourth segment, and in front of the next pair of lateral appendages 

 only one opening was found , its fellow of the opposite side or any 

 trace of it being wanting. 



29* 



