labkali glands of simocephalus 225 



On the 1^'ungtion of the Labral Glands. 



Home preliminary experiments of staining 8imocephalus 

 intra vitam suggested that further investigations might 

 ekicidate the functions of the labral glands. The experiments 

 which were accortlingly carried out did not prove of much use 

 in the direction expected, but were hiteresting and will be 

 described here. 



Fischel (6) describes experiments on intra vitam staining 

 using, among other stains, alizarin, neutral red, Bismarck 

 brown, Nile blue sulphate and hydrochloride. In repeating 

 his experiments using the stains named, the only stains with 

 which successful results were obtained were neutral red and 

 Bismarck brown. It ma}^ be mentioned that these two stains 

 were Grlibler's chemicals while the others were not. 



In I'ischel's figure of Daphnia magna stained intra 

 vitam with neutral red, there are figured two large red patches 

 in that region where the labrum should be drawn which 

 probably represent the labral glands. He states that these 

 glands are always to be found faintly stained in animals 

 stained intra vitam with neutral red. In adult Simo- 

 cephalus vetulus the most conspicuously-stained organs 

 in such animals are the labral glands and the body which 

 Fischel describes as a gland of unknown nature, which has 

 since been shown by Langhans (10) to be the end-sac of the 

 shell gland, and both these stain intensely. In the labral glands 

 both proximal and distal groups stain, but the duct-cell 

 remains unstained. The connexion between the anterior 

 and posterior pairs of cells of the distal group appears very 

 distinctly, and was at first thought to be a distinct duct. In 

 the gland-cells there appear accumulations of an intensely 

 staining material — these accumulations being often as large 

 as the nuclei of the cells. The reservoir of secretion which can 

 be seen in the living animal remains unstained. 



Fischel maintains that the staming with neutral red is not 

 due to the staining of passive metabolic products but to the 

 staining of preformed elements in the protoplasm. In support 



