EXCRETORY ORGANS. 



695 



The remainder of the 



into the Wolffian duct (fig. 390, px\ 

 vesicle becomes converted 

 into a Malpighian body (ing). 

 By the first of these changes 

 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 FIG. 390. LONGITUDINAL VERTICAL 



anterior part of the excretory SECTION THROUGH PART OF THE MESO- 



. NEPHROS OF AN EMBRYO OF SCYLLIUM. 



organs in the adult, and most The figure contains two exampks of the 



probably in the hinder part, budding of the vesicle of a segmental tube 



-, , . (which forms a Malpighian body in its own 



yet It seems almost certain seg ment) to unite with the tubulus in the 



that the secondary and ter- preceding segment close to its opening into 



the \\ olffian (mesonephric) duct. 

 tiary Malpighian bodies Ot ge. epithelium of body-cavity; st. peri- 



the majority of segments are ton ? f al fu , nnel of ^mental tllbe th its 



J peritoneal opening; nig. Malpighian body ; 



developed from its persisting px. bud from Malphigian body uniting with 

 11-1 , T^ i r i preceding segment. 



blind end. Each of these 



secondary and tertiary Malpighian bodies is connected with a 

 convoluted tubulus (fig. 391, a.uig), 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 



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. 



st.o. peritoneal funnel; p.mg. primary Malpighian body; a.uig. accessory Mal- 

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



