Scientific Lectures. 29 



The food of the polyp is received into the cavity of its body, and 

 there, thougli there is no visible digestive apparatus, it is nevertheless 

 digested. But, curiously enough, if the animal be turned inside out, 

 eo that what was its exterior surface becomes its stomach lining, it 

 manifests no inconvenience. Its food is received and digested quite 

 as well as before. 



To return, once more to tlie veojetable world. The lisfbt which the 

 microscope has tlirown upon the processes of reproduction of crypto- 

 gamic vegetation is very remarkable. Before the application of the 

 instrument to the study of these organisms, plants of this series were 

 supposed to form an exception to the law which governs vegetable 

 reproduction generally. In all of them, however, have been clearly 

 recognized, by the aid of this powerful instrument of investigation, 

 the entire apparatus which is so conspicuous in the anthers and the 

 pistils of the phanerogamic series, so that the seeming exception does 

 not exist. It has been proved also, that among the fungi different 

 forms of fructification appear in the same individual, and some 

 reason exists for believing that mici'oscopic fungoid vegetation is in 

 great measure determined in all the visible forms of its development, 

 by the conditions to which the ditierent germs may be subjected. 

 The number of sporules which a single fungus may produce is beyond 

 computation. It has been calculated, says Dr. Carpenter, that a 

 single individual of the puff-ball tribe may send forth no fewer than 

 10,000,000 ; but this seems to me to be a number far below the real 

 mark. " Their minuteness," the same writer continues, " is such 

 that they are scattered through the air in the condition of the finest 

 possible dust ; so that it is diificult to conceive of a place from which 

 they should be excluded. Hence we are not obliged to suppose that 

 distinct germs are floating about in the atmosphere, for all the forms 

 of fungous vegetation which appear to be of different species, and 

 whicli are only found in particular situations — \\\e puccinia rosae, for 

 instance, only upon rose bushes ; the Isariah felina^ only on the 

 excretions of cats in humid and obscure situations, and Oxygena exujna 

 upon the hoofs of dead horses ; but are warranted in believing that 

 the real variety of germs is comparatively small, and that the facts 

 just stated only indicate the modifying influence of the circumstances 

 under which they are developed." 



This view gives a seeming of probability to the opinion entertained 

 by some microscopists, that the fungoid vegetation which attends 

 many forms of animal aud vegetable disease is not so much a cause 



