1S93.I MICROSCOriCAL JOURNAL. 187 



Iiifiisori:!, within tlic five pouclics; of tlic stomach of the Echin- 

 oiliTiiiP, ill thr sej^incntal or<;:iiis of the leech«^s, of tho Oligo- 

 cliMota and of the Polychaota. 



Ciridiths of I'Minliurudi. has (Icnion^tiatrd the presence of 

 muroxiiK? in the contractile vesicles of Anuvha, of P(ir(im.frcium 

 and of Vortirelht. The process is to place a nuniher of the ani- 

 mals on a slide and to cover as usual. They are then killed hy 

 alcohol, which is to he followed by nitric acid. The slide i.s 

 gently warmed and ammonia introiluce(l, wiien, if the experiment 

 succeeds, the purple, prismatic crystals of murexide will make 

 their appearance in the contractile vesicle, showing that uric 

 acid had been present there. I do not think that a gas could 

 hold uric acid in solution any more easily than it could be 

 stained. 



"Through all the multitudinous changes " says Griffiths 

 "that have taken ))lace during the lapse of ages, in the develop- 

 ment of the mammalian kidney, we find tliat the physiological 

 functions are the same as occur in its original or primitive form 

 as represented in the Protozoa. It is not going too far to say, 

 that within these lower forms of animal lif-:! we have all the 

 necessary mechanism for the creatures to breathe, digest and 

 excrete. The only difJerence is that in the Protozoa the cell 

 performs numerous functions, whereas in the Vertebrata these 

 functions are localized in special organs.'' And Huxley says, 

 " * * * * the vertebrate kidney is an extreme m )ditication of 

 an organ, the primitive type of which is to be found in the or 

 gan of Bojanusofthe Mollusk, and in the segmental organ of the 

 Annelid ; and, to go still lower, in the water-vascular sys- 

 tem of the Turbellarian. And this, in its lowest form, is so 

 similar to the more complex conditions of the contractile 

 vacuole of a Protozoon, that it is hardly straining analogy too 

 far to regard the latter as the primary form of uropoetic as well 

 as of internal respiratory apparatus." 



Many theories have been propounded as to the final disposal 

 of the watery contents of the vesicles. Those that think the 

 contents are a gas, as Dr. Albert Schneider (Amer. Mo. Micro. 

 Journal, March, 1893), is fully convinced that they are and that 

 this gas is forced into the general system by the pulsations of 

 the organ, would do well to study the optical action of a gas- 

 bubble and of a drop of liquid enclosed within the endoplasm 



