ON PABAWRIGHTIA ROBUSTA. 205 



also for the centi-al bodies. By means of this stain the outei* 

 envelope of the capsule, which generally appears homo- 

 geneous, is shown to be finely laminated. 



Methyl eosin does not stain the capsule or the perisarc of 

 the hydroid to any extent. 



Congo red tends to stain the inner envelopes of the capsule 

 more than the outer sheath. All the tissues of the hydroid, 

 including the perisarc, are stained. On faintly acidulating- 

 the pi'eparation the perisarc becomes blue, while the capsules, 

 the mesoglea, and the rest of the tissues of the hydroid 

 remain red. 



Mr. Arnold Cooper has kindly tested for me the eifect of 

 the capsules on polarised light. He finds that they sometimes 

 possess slight depolarising power. The innermost layer of 

 the capsule immediately surrounding the central bodies ap- 

 pears generally to possess this power to the greatest extent. 

 The central bodies themselves remain dark. In some capsules 

 areas of light of different sizes appear in various parts of the 

 laminations. Perhaps this is due to stresses and sti"ains set 

 up in the substance of the ca]isule during its growth. The 

 perisarc, especially the innermost layer, and also the mesoglea 

 may at times possess a certain amount of depolarising power. 



In all the tests that have been applied, the capsules, the 

 mesoglea, and the perisarc react very similarly, and it is 

 possible that they may all consist of somewhat analogous 

 substances; but the capsules are certainly harder and more 

 brittle than either the inesoglea or the perisarc. 



It would appear probable that the organism gains entrance 

 into the gonophore when the latter is in the form of a bud, 

 for at this stage the young gonophore is practically naked, 

 as the covering membrane is excessively thin. 



The central body is possibly a Schizophyte, and the lami- 

 nated capsules recall Leuconostc; but in the present case 

 the capsules are hard and not gelatinous. 



The formation of a limited number of somewhat larg-e 

 spore-like bodies, with the disappearance of the middle 

 portion of the capsule and the greater number of the cocci. 



