SPORE-FORMATION. 25 



rule, after division, the micro-organisms separate, but the 

 contrary also occurs in the case of bacterial groupings, as 

 where, for example, chains of cocci or bacilli are present. 

 Under definite conditions of nourishment there occurs in 

 bacteria, vibriones, and higher fission-fungi, the formation 

 of longer threads, which further may always again break 

 up into segments. According to all the recent observa- 

 tions, the division of the cells proceeds from the outer pro- 

 toplasmic layer. 



Although longitudinal growth with transverse fission is 

 the rule for the host of bacteria, ^ still in certain families — 

 for example, sarcina — there occurs a regular division in 

 three main planes, and at least occasional division in two 

 planes at right angles to each other is observed in very dif- 

 ferent bacteria, — for example, in streptococci, — whereby 



Fig. 8. — ^Artkrospores of the vibrio oholerae (after Hiippe). 



there may be produced cells with four parts and forkings 

 of the chains. (Compare Fig. 2.) 



From the ordinary vegetative multiplication, propagation 

 by spore=formation is to be distinguished. To-day there 

 are recognized: (1) Endospores — strongly refracting oval 

 or round bodies, situated in the interior of cells, which, as 

 a rule, possess considerable resistance to injurious agencies 

 (heat, drying, chemicals); and (2) arthrospores (De 

 Bary, Hiippe) — i. e., bud-like constrictions of the ends of 

 the cells. Also these (Fig. 8) should be characterized by 

 increased resistance, yet recent authorities have never ac- 

 knowledged that the proof of resisting arthrospores has 

 succeeded without objection. (Compare Vib. cholerseand 

 Strept. pyogenes.) 



1 A longitudinal division in bacilli, although rare, is undoubtedly 

 observed (Babte, Z. H. xx, 412). Stellate divisiorrhas been observed 

 by MetschnikofE in a sporulating organism named ' ' Pasteuria, ' ' but 

 it scarcely belongs among the bacteria in the restricted sense. 



