OF ARTS AND SCIENCES. 145 



there are innumerable mesoblasts in the parent cells; and after the 

 latter have congregated to form the different layers of the incipient 

 organs of the embryo, and burst, the former unite side by side, and thus 

 become the original cells of the young tissues. 



'' I feel that I cannot urge too strongly the utmost necessity of study- 

 ing living beings as nearly in a state of nature as is possible ; to at- 

 tempt this by all available means and contrivances, and, above all, 

 patiently, not begrudging the time, because more numerous observa- 

 tions might be obtained by making a piecemeal and hurried show of 

 dismembered Nature. 



" It would certainly be more profitable, as far as living beings are 

 concerned, if the whole world of science should, for a while at least, in- 

 vestigate exclusively the few transparent animals that may be obtained, 

 than work over the numbex'less opaque ones which require the dissect- 

 ing-knife. The first having been investigated, the knowledge of them 

 would assist us the better to interpret the features and relations of the 

 tissues, which we would be obliged to study in a disconnected state, just 

 as fossils are recognized and restored by the comparative anatomist 

 after a careful research among living models. 



" I have been anxious to present this communication, and to have it 

 recorded, because certain microscopists, who are considered as high 

 authority both in England and in this country, have attempted to de- 

 preciate the value of the flat field and wide angle of aperture in the 

 study of living objects. This is a little remarkable, since it comes from 

 a country where, until recently, the most finished microscopes of this 

 kind were made, and where they are now to be found in large num- 

 bei's. I will read a few passages, which may be found on page 196 of 

 Dr. Carpenter's work on the microscope. He says : ' The author 

 feels it the more important that he should express himself clearly and 

 strongly on this subject, as there is a great tendency at present, both 

 among amateur microscopists and among opticians, to look at the at- 

 tainment of that " resolving power " which is given by angular aperture, 

 as the one thing needful ; those other attributes which are of far more 

 importance in almost every kind of scientific investigation, being com- 

 paratively little thought of ; and he therefoi-e ventures here to repeat 

 the remarks he made upon this subject, in his recent Presidential Ad- 

 dress to the Microscopical Society, of the correctness of which he has 

 been since assured, by the approval of many of those who have most 



VOL. IV. 19 



