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complete, as just described, but the two masses, instead of separating 

 wholly, again approached each other, and nearly recovered their 

 original shape. 



From the manner in which solid particles pass through these struc- 

 tures, and the rapidity with which the whole organism becomes sub- 

 divided, it is reasonable to infer that they have no proper integument^ 

 especially as the microscope fails to reveal such a structure. 



Professor Henry James Clark said that Actinophrys was particular- 

 ly interesting, as manifesting a step higher than the simple homomor- 

 phous organization of Amoeba, as described by Prof Wyman. Prof 

 Clark referred to Kolliker's observations in 1849, as recorded in the 

 Zeitschrift fiir Wissenschaftliche Zoologie, and showed that, even sup- 

 posing KoUiker to be correct, the division of the mass of the body into 

 an exterior and interior portion, the former containing much larger 

 vacuoles than the latter, indicated a heteromorphous organization, and 

 tending toward specialization of parts. He also added that he could 

 not agree with Kolliker, that Actinophrys is a homomorphous mass 

 with vacuoles, but that he was convinced that the so-called vacuoles 

 of the outer and inner layers, are true cells, with a distinct wall 

 about them; a wall that could be easily recognized with the help 

 of the better sort of microscope objectives of the present day. Owing 

 to the exceeding transparency of the organism, no ordinary objective 

 will show the walls; but, with a one-quarter inch lens, of one 

 hundred and fifty degrees angular aperture, made for him, last June, 

 by ToUes, of Canastota, N. Y., he had no difficulty in working, with 

 the proper adjustment and corrections, through a sufficient depth of 

 water to completely cover the Actinophrys (A. Eichornii), and could 

 readily detect the walls, not only of the superficial cells, but also of 

 the innermost ones.* 



* The unprecedented working distance, whicli accompanies the great angle of 

 aperture in the above-mentioned lens, prompts me to speak more fully of its 

 excellence. It has been the chief desideratum of naturalists to obtain a large in- 

 crease in the working distance of those h'nses which have a greataiigleof aperture ; 

 but, hitherto, the latter condition has seemed to involve necessarily an excessively 

 short working distance, and consequently great inconvenience in the investigation 

 of all bodies which are not correspondingly thin. Tlie idea of studying marine ani- 

 mals in their native element, with such leases, could never be indulged in, for fear 

 of ruining the objectives, by contact with salt water. At last, we are relieved from 

 this restraint, for within the last four or five years a great improvement has been 

 made in this respect by opticians, at least by Mr. Tolles. The most recently con- 

 structed lens which I have received from that gentleman was made last .June; it is 

 a one-quarter inch objective, with an angular aperture of one hundred and fifty de- 

 grees, and a most unexpected working distance of one-fiftieth of an inch for un- 

 covered bodies. By experiment, 1 also find that it works through a glass covering, 

 fully one-fortieth of an inch thick, and with some room to spare above that. The 

 working distance through water I have not measured accurately; but that can be 

 inferred from the difference between its refraction and that of glass. The defining 

 power of this lens is certainly unsurpassed, if not unequalled. 



