TRANSACTIONS OF THE SECTIONS. 117 



suit of this restoration became apparent in the foundation of a new era in the 

 knowledge of the minute characters of textural structm'e, under the joint guidance 

 of Robert Brown and Ehrenberg, with contributions from many other observers, 

 so as at last to have almost entitled this branch of inquiry to its designation, 

 by ]Mr. Huxley, of the exhaustive investigation of structm-al elements. All who 

 hear me are aware of the influence which, from 1839 onwards, the researches of 

 Schwann and Schleiden exerted on the progress of Histology and the views of 

 anatomists and physiologists as to the structure and development of the textures 

 both of plants and animals, and the prodigious increase which followed in varied 

 microscopic observations. It is not for me here even to allude to the steps of that 

 rapid progress by which a new branch of anatomical science has been created ; nor 

 can I venture to enter upon any of the interesting questions presented by this de- 

 partment of microscopic anatomy ; nor attempt to discuss any of those difiicult 

 problems possessing so much interest at the present moment, such as the nature of 

 the organized cell or the properties of protoplasm. I would only remark that it is 

 now very generally admitted that the cell-wall (as Schwann indeed himself pointed 

 out) is not a constant constituent of the cell, nor a source of new production, 

 though stiU capable of considerable structm'al change after the time of its first 

 formation. The nucleus has also lost some of the importance attached to it by 

 Schwann and his earlier followers, as an essential constituent of the cell, while 

 the protoplasm of the cell remains in undisputed possession of the field as the more 

 immediate seat of the phenomena of growtli and organization, and of the contrac- 

 tile property which forms so remarkable a feature of their substance. I cordially 

 agree with much of what Mr. Huxley has written on this subject in 1853 and 

 1869. The term physical basis of life may perhaps be in some respect objection- 

 able ; but I look upon the recognition of protoplasm which he has enforced as a 

 most important step in the recent progTess of histology, adopting this general 

 term to indicate that part of the organized substance of plants and animals which is 

 the constant seat of the growing and moving powers, but not implying identity of 

 nature and properties in all the variety of circumstances in which it may occur. To 

 Haeckel the fuller history of protoplasm in its lowest forms is due. To Dr. Beale 

 we owe the minutest and most recent investigation of these properties by the use of 

 maguifj'ing-powers beyond any that had previously been known, and the success- 

 ful employment of reagents which appear to mark out its distinction * fi-om the 

 other elements of the textures. I may remark, however, in passing, that I am 

 inclined to regard contractile protoplasm, whether vegetable or animal, as in no 

 instance entirely amoi-phous or homogeneous, but rather as always presenting some 

 minute molecular structure which distinguishes it from parts of glassy clearness. 

 Admitting that the form it assumes is not necessarily that of a regular cell, and 

 may be various and irregular in a few exceptional instances, I am not on that ac- 

 count disposed to give up definite structure as one of the universal characteristics 

 of organization in living bodies. I would also suggest that the terms formative 

 and non-formative, or some other such, would be preferable to those of " living and 

 dead," employed by Dr. Beale to distinguish the protoplasm from the ceU-wall or 

 its derivatives, as these latter terms are liable to introduce confusion. 



To the discoveries in embryology and development I might ha^e been tempted 

 to refer more at large, as being those which nave had, of all modern research, 

 the greatest effect in extending and modifying biological views, but I am 

 warned from entering upon a subject in which I might trespass too much 

 on j'our patience. The merits of Wolft" as the great leader in the accurate ob- 

 servation of the phenomena of development were clearly pointed out by Mr. 

 Huxley in his presidential address of last year. Under the influence of Dollinger's 

 teaching, Pander, and afterwards Purkinje, Von Baer, and Rathke, established 

 the foundations of the modern history of embryolog^l^ It was only in the year 

 1827 that the ovum of mammals was discovered by Von Baer; the segmentation 

 of the yelk, first observed by Prevost and Dumas in the frog's ovum in 1824, was 

 ascertained to be general in succeeding years ; so that the whole of the interesting 

 and important additions which have followed, and have made the history of em- 

 bryological development a complete science, have been included within the eventful 

 * Under the appropriate name of " bioplasm," 



