vl] the fresh-water polypes. 357 



a. Small orgafiisms; especially Etitomostraca and other 

 small Crustacea. When present one such will gene- 

 rally be found, tightly embraced by the endoderm. 



Examine under a high power and look for evidences 

 of digestion {infra-enteric) and assimilation. 



b. Smaller orgafiisms ; especially Infusoria, Diatonis, and 

 the like. Frequently to be met with in the central 

 cavity; they may however be found, unchanged or in 

 process of digestion {int7-a-celliilar\ within the indivi- 

 dual cells of the endoderm. 



8. The reproductive organs. (Cf Sect. 2. a. e). 



a. The testes; small conical colourless eminences below 

 the point of attachment of the tentacles, more rarely 

 irregularly scattered over the whole body. 



Gently flatten out a testis in eosin or magenta by 

 pressure on the coverslip, and examine with a high 

 power. According to its state of maturity the follow- 

 ing contents will be found in it — 



a. A collection of the smaller ectoderm (interstitial) 



cells of variable shape. 

 /?. The same, but having become ovoidal and hyaline. 



y. Cells otherwise like y8, but with a long filament 

 proceeding from them. 



8. Ripe spermatozoa ; bodies consisting of a very small 

 oval nucleated head to which a very delicate 

 flagellum is attached, by the movements of which 

 they swim about in the water. They may fre- 

 quently be seen in motion within the unruptured 

 testis. 



b. The ova?'ies; one or more in number, larger than a, 

 and situated near the base of the polype. 



