EXCRETORY ORGANS. 



695 



into the Wolffian duct (fig. 390, px). The remainder of the 

 vesicle becomes converted 

 into a Malpighian body (mg}. 



By the first of these changes 10^-4 M @W>f 

 a tube is established con- 

 necting each pair of segments 

 of the mesonephros, and 

 though this tube is in part 

 aborted (or only represented 

 by a fibrous band) in the 

 anterior part of the excretory 

 organs in the adult, and most 

 probably in the hinder part, 

 yet it seems almost certain 

 that the secondary and ter- 

 tiary Malpighian bodies of 

 the majority of segments are 

 developed from its persisting 

 blind end. Each of these 



FIG. 390. LONGITUDINAL VERTICAL 

 SECTION THROUGH PART OF THE MESO- 

 NEPHROS OF AN EMBRYO OF SCYLLIUM. 



The figure contains two examples of the 

 budding of the vesicle of a segmental tube 

 (which forms a Malpighian body in its own 

 segment) to unite with the tubulus in the 

 preceding segment close to its opening into 

 the Wolffian (mesonephric) duct. 



ge. epithelium of body-cavity; st. peri- 

 toneal funnel of segmental tube with its 

 peritoneal opening; mg. Malpighian body; 

 px. bud from Malphigian body uniting with 

 preceding segment. 



secondary and tertiary Malpighian bodies is connected with a 

 convoluted tubulus (fig. 391, a.mg), which is also developed from 

 the tube connecting each pair of segmental tubes, and therefore 

 falls into the primary tubulus close to its junction with the 



st.c 



w.d 



FIG. 391. THREE SEGMENTS OF THE ANTERIOR PART OF THE MESONEPHROS OF A 

 NEARLY RIPE EMBRYO OF SCYLLIUM CANICULA AS A TRANSPARENT OBJECT. 

 The figure shews a fibrous band passing from the primary to the secondary Mal- 

 pighian bodies in two segments, which is the remains of the outgrowth from the 

 primary Malpighian body. 



sf.o. peritoneal funnel; p. ing. primary Malpighian body; a.mg. accessory Mal- 

 pighian body; w.d. mesonephric (Wolffian) duct. 



