ZOOLOGY AND BOTANY. MICROSCOPY. ETC. 749 



" lobe " (Liippchen) and " terminal sack " (Endsiickchen) applied to it by 

 Wassiliew and Grobbeu are misleading, 



llie green substance consists of generally homogeneous cells, with a 

 delicate contour, a well-defined nucleus, one or more pigment globules, 

 which in some cases collect and escape at one pole. They closely resemble 

 similar globules found in the white substance. They are apparently a 

 secretory modification of the protoplasm. The cells are very readily 

 broken ; liberated nuclei occur all over the preparation, and exhibit among 

 the numerous granules two or three sharply defined " nucleoli." The very 

 delicate cell-membrane can only withstand dilute acetic acid. The green 

 substance does not exhibit " the small blind sacks " which Huxley de- 

 scribes. Nor is there any hint of a cuticle formed by the cells, as Hiickel, 

 Grobben, and Wassiliew assert. Nor does the epithelium of either white 

 or yellow-brown substance exhibit any such structure. The cells of the 

 green substance are, however, seated on a fine, delicate, nucleated tunica 

 propria. The lumen of the tube forming the green substance is either 

 empty, or filled with a peculiar meshwork arising from the protoplasm of 

 the modified surrounding cells. The various coils of the tube are separated 

 by connective tissue, which bears vessels, and includes cavities which 

 appear to contain blood-corpuscles. In some cases Herr Rawitz detected 

 cells which seemed to him to be ganglionic. 



The white substance is characterized by the absence of the green pig- 

 ment, and by the glancing appearance of the epithelium. The cells gene- 

 rally resemble those of the green portion. Two different regions can be 

 distinguished, (a) that which forms a continuation of the green substance, 

 and (6) the terminal portion — the white substance proper. The epithelium 

 of the former is very characteristic. The cells appear to consist of two 

 portions — the basal and larger taking up a varying amount of stain, the 

 other remaining colourless, but bounded towards the lumen of the tube by 

 a very narrow fringe of stained protoj)lasm. The nucleus lies in the stained 

 portion, and in such a way that the pole turned from the tunica propria 

 exactly marks the boundary between modified and unmodified protoplasm. 

 The epithelium of the white substance proper has a quite different appear- 

 ance. The cells are flatter, the protoplasm without differentiation, the 

 nuclei elongated oval, the limits of the cells obscure. The disruption of 

 epithelium noted above in the green substance never occurs in either of the 

 other portions. The connective tissue between the adjacent coils of the 

 tube is less developed than in the green substance ; it is reduced to narrow 

 strands ; the nuclei are smaller and scarcer ; the presence of blood-vessels 

 is at least doubtful. 



The yellowish-broivn substance owes its colour, not as Grobben reports, to 

 a deposition of irregular bodies of a yellowish-brown colour in the proto- 

 plasm, but to the presence of more or less intensely straw-coloured nuclei. 

 These coloured nuclei are, however, in the minority ; in most of the cells 

 the nuclei are colourless. Otherwise the cells resemble those of the green 

 substance. As in the latter, numerous elements occur containing abundant 

 glancing globules. These are in all probability the result of secretion. 

 The green and the yellowish-brown portions thus agree, and together differ 

 from the white portion. The connective-tissue and contained vessels are 

 very sparsely developed. 



The secreted products found in the white portion are round dull globules, 

 with a sharp contour, and transparent homogeneous appearance. They 

 occur singly or in groups. Of rarer occurrence, are club-shaped products, 

 sometimes of very considerable size. They then exhibit a double contour, 

 a yellowish-green colour, and a brighter well-defined spot in their expanded 



1887. 3 D 



