The President's Address. By the Bev. W. H. Dcdlinger. 199 



even most markedly, if the thin film of fluid be allowed to partly 

 evaporate while the object is carefully kept in the field and the 

 acetic acid methyl-green be then run under. The investing 

 membrane or wall is seen in plate VIII. fig. 2. At the same time, 

 as well by subsequent siruilar treatment as by patient study of the 

 hving form, a distinct granular condition becomes apparent in 

 what was the homogeneous hyaloplasm. 



My deep desire was to study this change as it progressed in the 

 living organism. Keagents and stainings are invaluable: but on 

 minute structures such as these their action is too violent, and cannot 

 with our present knowledge be accurately or with strict certainty 

 interpreted. At least, if the study can be effected optically in the 

 living form it is an additional advantage and control, and leads to 

 more delicate and sure results. Fortunately the nucleus is in an 

 absolutely inactive state ; hence I could use homogeneous lenses, and 

 every variety of illumination, without fear either of losing or injuring 

 the object : and after the first twenty minutes of arrest of outward 

 growth I was enabled to make out a distinct granulation, merging 

 almost into a plexus during the next thirty minutes. Its delicacy 

 is extreme, but there is a manifest difference in the refrangibihty 

 of the granular structure, and the general hyaloplasm of the 

 nucleus. I do not for a moment assume that the full form of this 

 plexus structure has been made out, but as well as I can represent 

 so delicate a condition it is shown in plate VIII. fig. 3. It can be 

 emphasized in one sense by the use of acetic methyl-green : but 

 it is also distorted by a kind of coagulation, by means of which all 

 its true character is gone. But by the use of the full aperture of 

 the lens (1/20 1-5 N.A., 1/50 1-37 N.A., and 1/12 1-5 N.A.) 

 and the employment of delicate means of illumination, upon which 

 so much depends, it is possible to clearly see the growth in the 

 living nucleus of the plexus-like or intertwisted structure seen in 

 plate VIII. fig. 3. But it is not easy either to figure or describe 

 the exact state of the nucleus that is disclosed. It is suggestive, 

 however, of a complex weaving or plaiting ; and runs throughout 

 the contents of the nuclear body. 



Now, it is when this condition of the nucleus is fully attained 

 that the growth of the general organism recommences. A cloudy 

 white film of extreme delicacy first presents itself outside the 

 margin of tbe nucleus, as seen in plate VIII. fig. 4, and this rapidly 

 widens, as in figs. 5 and 6, ibid., taking the normal form of the 

 organism in a longer or shorter time, until the adult size is reached 

 and motion commences. 



But there was one other point of the deepest interest. It was 

 that I was enabled to determine that the flagellum or flagella, in 

 each instance, arose in the nucleus; and it was, or they were, 

 carried outwards with far greater rapidity than the somatic sarcode, 



