DEVELOPMENT OF ELASMOBRANCH FISHES. 255 



a portion of the Wolffian body with three complete segments and 

 part of a fourth. If one of these be selected, it will be seen to 

 commence with (1) a segmental opening, somewhat oval in 

 form (st.o) and leading directly into (2) a narrow tube, the 

 segmental tube, which takes a more or less oblique course back- 

 wards, and, passing superficially to the Wolffian duct {w. d), opens 

 into (3) a Malpighian body {p.mg) at the anterior extremity 

 of an isolated coil of glandular tubuli. This coil forms the 

 fourth section of each segment, and starts from the Malpighian 

 body. It consists of a considerable number of rather definite 

 convolutions, and after uniting with tubuli from one or two 

 (according to size of the segment) accessory Malpighian bodies 

 (a. mg), smaller than the one into which the segmental tube 

 falls, eventually opens by a (5) narrowish tube into the Wolffian 

 duct at the posterior end of the segment. Each segment is 

 completely isolated (except for certain rudimentary structures 

 to be alluded to shortly) from the adjoining ones, and never has 

 more than one segmental tube and one communication with the 

 Wolffian duct. 



The number and general arrangement of the segmental 

 tubes have already been spoken of. Their openings into the 

 body cavity are, in vScyllium, very small, much more so than 

 in the majority of Elasmobranchs. The general appearance of 

 a segmental tube and its opening is somewhat that of a spoon, 

 in which the handle represents the segmental tube, and the bowl 

 the segmental opening. Usually amongst Elasmobranchs the 

 openings and tubes are ciliated, but I have not determined 

 whether this is the case in Scy. canicula, and Semper does not 

 speak definitely on this point. From the segmental openings 

 proceed the segmental tubes, which in the front segments have 

 nearly a transverse direction, but in the posterior ones are 

 directed more and more obliquely backwards. This statement 

 applies to both sexes, but the obliquity is greater in the 

 female than in the male. 



As has been said, each segmental tube normally opens 

 into a Malpighian body, from which again there proceeds the 

 tubulus, the convolutions of which form the main mass of 

 each segment. This feature can be easily seen in the case 

 of the Malpighian bodies of the anterior part of the Wolffian 



