1002 RECOKD OF CURRENT RESEARCHES RELATING TO 



increase so as to resume their primitive form, and then in their turn 

 divide when they have reached their full size. Sometimes the entire 

 mass is naked ; its contour is formed simply of the extremities of the 

 peripheral cells which are bound together by the interstitial gelatinous 

 substance. Sometimes, on the contrary, it is enveloped by a resisting 

 membrane of a gelatinous appearance, which, after each augmentation 

 of the contents, develops between the two halves, and then divides so 

 as to clothe them completely and independently after their separation. 



The segmentation of the entire body takes place either in one 

 direction only, and the small masses remain, at least for a time, 

 united like bead-work, or in two directions in the same plane, and 

 the masses spread out side by side in the form of a membrane ; or 

 finally, in three directions, and the masses are superposed in a solid 

 mass, and form nodules of a smaller or larger size. 



Thus are formed aggregations of cells, derived from one primitive 

 parent cell, and following henceforth a common law ; and these cells, 

 in their form, their mode of increase, their successive divisions, and 

 the relations which they maintain towards one another, behave like 

 so many simple cells, sometimes naked, sometimes enveloped in a 

 membrane. They constitute, in fact, cells of a second order, com- 

 posite cells, something like those compound bodies which, in chemical 

 combinations, play the part of simj^le bodies. By careful crushing, 

 these colonies can be decomposed ; when the isolated cells, continuing 

 to increase as when they formed part of the colony, soon again con- 

 stitute new societies, which again carry on their normal development. 



In further investigating the form of the primitive cells, the form 

 of the colonies, or cells of the second order, the presence or absence 

 of a general membrane, and the relative disposition of the colonies 

 after their division, characters may be obtained of a certain number of 

 genera and species ; and the author proceeds briefly to define the types 

 best known to him, and the development of which he has been able to 

 follow. They arrange themselves in two groups, according as the 

 colony is or is not provided with an enveloping membrane. 



1. Naked Colonies. — The colony is composed either of cylindrical 

 cells similar to those of Bacterium and Bacillus, or of spherical cells 

 similar to those of Micrococcus. The former are united into the 

 genus Polyhacteria, the latter into the genus Punctula. 



Polyhacieria. — In the decoction of horse-dung which is frequently 

 employed for the production of fungi, M. Van Tieghem has often met 

 with a Polyhacteria, in which the naked, colourless, oval colonies, 

 composed of small rods aggregated in every variety of way, always 

 divide transversely in the same direction, and remain end to end in the 

 form of a frequently sinuous chain. This chain proceeds from the 

 increase and division of a single mass, and this primitive mass is 

 again entirely derived from a spore or a rod, as the writer has many 

 times demonstrated by tracing the development of this minute organism 

 in cell cultures, which is not unattended with difficulty. It may be 

 called Polyhacteria catenata. 



In another species the rods are of a sulphur-yellow colour, the 

 colonics rounded or polyhedral, and segmentation takes place in two 



