360 SUMMARY OF CURRENT RESEARCHES RELATING TO 



structure of plastids precisely similar to those propounded in 1879 

 by Maggi. In his view the protoplasm and plasson are made up of 

 numerous simple albuminoid particles, which he agrees with Maggi 

 in naming jplastidules and which represent the simplest morphological 

 elements. The simplest forms of these plastidules, the so-called pro- 

 toplastidules, are said to be the granules devoid of independent motion 

 which are found in organic infusions ; with these may perhaps be 

 ranked as structures of similar morphological value, the free solitary 

 spherical Bacteria, the Cocci, and Micrococci. If these protoplasti- 

 dules become differentiated in such a way as to form around them- 

 selves parts of unequal physiological values, there arise the autoplasti- 

 dules, among which must be included the simple Microbacteria, such 

 as Bacterium termo, the Monococci and Monobacteria of Billroth, the 

 Desmobacteria (Bacillus), and the Spirobacteria (Spirillum). By 

 colonial growth, on the other hand, the protoplastidules give rise to 

 symplastidules, among which are placed the social forms of the 

 Bacteria, as the Diplobacteria, the Strepto-, Glio-, and Petalobacteria, 

 and also the Amj^hiasters (Kernspindeln), and stellate figures of cells 

 in process of division. A combination of plastidules which are not 

 all developed in the same way forms a plastid. 



Differentiation generally takes place in a radiating manner, so 

 that an outer and an inner mass are formed, differing somewhat from 

 each other. The simpler forms are in this case the protoplastids, 

 which include the non-nucleate gymno- and lepo-cytodes, and the 

 simpler nucleate gymno- and lepo-cellulse. By further differentiation 

 these protoplastids result in aiitoplastids. The author considers 

 that the different layers of differentiated substance in a highly 

 developed autoplastid, viz. ecto-, meso-, entoplasm, nucleus, and 

 nucleolus, may be compared to so many cytodes concentrically 

 grouped; and thus an autoplastid of this kind is to be regarded 

 anatomically (though not genetically) as a colony of cytodes. 



The colonies of plastids are described as sijmplastids. The author 

 includes among them the Gregarinae. 



Eozoon Canadense.* — Professors King and Eowney deal with the 

 question of the organic nature of Eozoon and of simulation of organ- 

 ized structures generally, their opinion being decidedly in favour of 

 its mineral origin. 



In the first place they state that the " typical nummuline wall " 

 is a pectinated form of chrysolite, due to modification of that 

 allomorph of serpentine, where the fibres of the mineral ultimately 

 become separated aciculfe with calcareous intorj)olations. The 

 " canal system, &c.," is rather more obscure in its origin. It is 

 frequently due to the peculiarities of a layer of flocculite (a non- 

 fibrous allomorph of serpentine), which on undergoing some solvent 

 or decreting process, is apt to be shaped into irregular configurations. 

 So likewise the " chamber castes " of the acervuline variety are 

 identical with the variously lobulated crystalloids characteristic of 



* King and Eowney, ' An Old Chapter in the Geological Eecord with a New 

 Interpretation ; or, Kock Metamorphism and its Kesultant Imitation of Organ- 

 isms.' 8vo, Van Voorst, 1881. See Geol. Mag., ix. (1882) pp. 231-6. 



