LABRAL GLANDS OF SIMOCEPHALUS 227 



fill effect on Bimocephaliis vetulus. No individual 

 of Simocephalus exspinosus was found to survive 

 a weak solution longer than twelve hours. In Simocephalus 

 vetulus the movements of the limbs is always retarded when 

 the animals have been in such a solution for about twelve 

 hours. Advantage was taken of this fact to study the move- 

 ments of the limbs during feeding. Usually, even if the stained 

 individuals are removed to pure water, they survive only a few 

 days. Sometimes, however, with young individuals they sur- 

 vive and completely lose all effects of the stain. No adults 

 have been obtained to survive long the effects of the stain, 

 but among these adults the stain often shows signs of disap- 

 pearing and yet the labral glands always remain as con- 

 spicuously stained as at first. It was thought from these 

 results that the labral glands might be partly the agents 

 causing the disappearance of the neutral red. However, 

 in the well-known experiment of feeding Daphnids on carmine, 

 while the end-sac of the shell gland is stained by the carmine 

 there is never any trace in the labral glands. This experiment 

 was also repeated with neutral red, Bismarck brown, Nile 

 blue sulphate and hydrochloride, using a filtered mixture of 

 the stain with milk to feed, but there was no indication as to 

 where the stain was excreted. 



Apparently with neutral red and Bismarck brown the staining 

 effect is not produced through the gut but the stain acts directly 

 through the cuticle. Thus young embryos in the brood-pouch 

 stain just as markedly as their parent. Both these stains 

 show a great affinity for yolk. Individuals with nearly fully- 

 developed embryos in the brood-pouch were stained in neutral 

 red for twenty-four hours. Those individuals were then 

 selected which had given birth to their brood, but had not 

 yet laid their next batch of eggs, and these had deeply-stained 

 ovaries. These were returned to fresh water. The eggs which 

 were subsequently laid were stained deep red. As these 

 developed the stain was seen to be confined chiefly to the yolk. 

 In most cases the adults died before giving birth to the young 

 but in a few cases the voung were born, but the adults never 



