108 ADAM SEDGWICK. 



the case, but here a regular series of primary Malpighian bodies 

 is present, and the glomerulus of the head-kidney may fre- 

 quently be seen in the same section as a Malpighian body. In 

 most sections the two bodies appear quite disconnected, but in 

 those sections in which the glomerulus of the Malpighian body 

 comes into view it is seen to be derived from the same formation 

 as the glomerulus of the head-kidney.'' 



The point which is left in doubt in the above description, viz. 

 as to whether the glomerulus constitutes a continuous structure, 

 is at once decided by a study of its development. 



I may here state that it is not a continuous structure, but 

 consists of a series of external glomeruli, each of which corre- 

 sponds and is continuous with the glomeruli of the Malpighian 

 bodies found in this part of the trunk. 



1 will commence the description of the development at the 

 time when the segmental tubes have reached the stage of devel- 

 opment figured by KolUker^ and myself.^ At this stage each of 

 them in the anterior region of the Wolffian body has the form of 

 an S-shaped string, with a narrow opening into the body cavity, 

 the lower limb of the S being formed by the intermediate cell 

 mass, and the upper limb by a column of cells which connects 

 the intermediate cell mass with the Wolffian duct. 



In the region where each external glomerulus is afterwards 

 found the openings into the body cavity, which are homologous 

 with the peritoneal openings of the segmental tubes in Elasmo- 

 brauchs, widen out very considerably, and a lumen is continued 

 from them into the intermediate cell mass on the one hand, and 

 on the other hand into the column of cells which forms the 

 upper limb of the S and connects the iiiter mediate cell mass with 

 the Wolffian duct.^ 



That part of the segmental tube which will afterwards become 

 a Malpighian body is therefore, in the region where an external 

 glomerulus will subsequently be formed, connected with the body 

 cavity by a short tube. This tube rapidly widens out, especially 



* ' Entwicklungsgeschichte des Menschen u. der hohereu Thiere,' p. 201, 

 2ud ed. 



2 ' Development of the Kidney, &c.,' p. 62 of '* these Studies," PI. VI, 

 fig. 1. 



' This may best be understood by exatnhiirg fig, 11, PI. VI, in my paper 

 already referred to. If the primary WolflBau tubule [t^i^), here represented, 

 were connected with the peritoneal epithelium at the point where the line 

 from wl^ cuts it, and it were open to the body-cavity at that point, an appear- 

 ance similar to that which I have attempted to describe would be obtained. 

 Or perhaps a better idea of the structure may be obtained from fig. 6, PI. 

 XX, in Balfour's 'Monograph on the Development of Elasmobranoh Fishes.' 

 If st were very short and wide, so that ?/i^ were widely open to the body- 

 cavity, the figure would resemble a developing Wolfiian tubule in this 

 anterior part of the chick's Wolffian body. 



