6 REPORT — 1879. 



suggesting, as it does, the idea of a hollow body or vesicle, this having 

 been the form under which it was first studied. The cell, however, is 

 essentially a definite mass of protoplasm having a nucleus imbedded in it. 

 It may, or may not, assume the form of a vesicle ; it may, or may not, 

 be protected by an enveloping membrane ; it may, or may not, contain 

 a contractile vacuole ; and the nucleus may, or may not, contain within 

 it one or more minute secondary nuclei or 'nucleoli.' 



Haeckel has done good service to biology in insisting on the necessity 

 of distinguishing such non-nucleated forms as are presented by Protamoeba 

 and the other Monera from the nucleated forms as seen in Amoeba. To 

 the latter he would restrict the word cell, while he would assign that 

 of ' cytode ' to the former. 2 



2 In every typical cell three parts may be distinguished. There is first the more 

 or less liquid granular protoplasm ; secondly the nucleus ; and thirdly an external 

 more firm zone of protoplasm, known as the ' cortical layer ' — the Hautschicht of the 

 German histologists. All these parts may be regarded as portions differentiated 

 out of the original simple protoplasm. Cells do not, however, always remain on a 

 stage of such simplicity as that presented by Ainceba. The nucleus is always at its 

 origin quite homogeneous, but as it increases in size it usually manifests a differen- 

 tiation resulting in a constitution which recent research has shown to be more 

 complex than had been previously supposed ; for we often find it to present 

 an external firmer layer, or nuclear membrane, including within it the softer nuclear 

 protoplasm, in which again a network of filaments has been in many instances 

 described. 



The structure of the nucleus has been quite recently studied by Flemming ( Arch, 

 f. Mikr. Anat. Band xvi. Heft 2. 1878), who has given particular attention to this 

 intranuclear network. He maintains that in its completed state the nucleus consists 

 of a parietal firm layer, which encloses, besides specially differentiated nucleoli, a 

 framework (Geriist) of filaments with a more fluid intervening substance. He 

 further insists on the fact that, with the differentiation of a nucleus, there is intro- 

 duced a chemical difference between its substance and that of the surrounding 

 cell-substance, as shown not only by a different behaviour of the nucleus towards 

 re-agents, but by an actually determined difference of chemical composition. 



Klein (Quarterly Joiirn. Mier. Sei. vol. xviii. p. 316) has shown that in the cells 

 of the stomach of Triton cristatus there is a delicate intranuclear network of fila- 

 ments in all respects resembling that described by Flemming ; and he further 

 maintains that the network of the nucleus is here continuous, through minute 

 apertures near the poles of the nuclear membrane, with a similar network in the 

 surrounding cell-substance. In this cell-substance he distinguishes two parts— the 

 homogeneous ground -substance and the intracellular network of filaments. 



Flemming, however, will not admit this connection between intra-nuclear and 

 intra-cellular filaments, and Schleicher, as the result of his very recent researches on 

 the division of cartilage-cells (Die Enwjielzelltheihmg, Arch, f . Mikr. Anat. Band 

 xvi. Heft 2, 1878), concludes that in these there is no true intra-cellular network, 

 the nucleus being here composed of a multitude of separate rodlets, filaments, and 

 granules surrounded by the nuclear membrane. 



The minute granules which are generally seen in the soft protoplasm of the cell 

 do not seem to be essential constituents. They are probably nutritive matter intro- 

 duced from without, and in process of assimilation and conversion into proper 

 protoplasm. Hanstein has distinguished by the term Metaplasm these granules 

 from the proper homogeneous protoplasm in which they are suspended. The 

 external cortical layer is quite destitute of them : on this devolves the property of 

 protecting the contents from the unfavourable action of outer influences, and to it 

 alone in plants is allocated the property of secreting the cellulose boundary wall. 



Several recent observers, but more especially Strasburger (Studien iiber das 

 Protoplasnia Jenaisehe Zeitschr. 1876), have described in the cortical layer of 

 various cells a radial striation, as if formed by excessively delicate rodlets (Stab- 

 chen), placed vertically to the surface and in close proximity to one another. He 



