[ 



1919] DRECHSLER— ACTINOMYCES 161 



aberrant type is seen in fig. 103, the fertile branches being short, 

 inserted at close, irregular intervals, and showing no spiral tendency; 

 while the axial filament is thick and abounding in spherical struc- 

 tures containing either deposits of metachromatic material or a 

 partial equatorial septum. 



In the dextrorse spiral hyphae of 1-8 open turns, 2.0-3 o ju in 

 diameter, the ellipsoidal spores, 0.8-0.9X1 o-i .6 ju, are produced 

 by the insertion of conspicuous septa, sometimes in association with 

 spherical structures. The presence of the latter (fig. 106), however, 

 is not here indicated by local distensions. Subsequently the cross- 

 walls undergo constriction and conversion to narrow connecting 

 isthmuses. In the aberrant fertile h>^hae (those without any 

 spiral tendency), sporogenesis appears to take place in a more 

 miscellaneous manner. Definite septa can rarely be distinguished, 

 the spores seeming to result from protoplasmic contractions. 



Isolated once from soil collected in Cambridge, Massachusetts. 



Summary 



1. The vegetative thallus of Actinomyces consists of a mycelium 

 composed of profusely branching hyphae, the terminal growing 

 portions of which are densely filled with protoplasm. Toward the 

 center of the thallus the vacuoles increase in size and may be 

 associated with the presence of metachromatic granules, the latter 

 having nothing in common with bacterial endospores or "micro- 

 cocci,'' for which they were mistaken by early observers. 



2. The vegetative mycelium attains an extent incomparably 

 greater than the branching figures recorded for bacteria of the acid- 

 fast group, and the hyphae lack the uniformity in diameter generally 

 characteristic of the Schizomycetes. 



3. The aerial mycelium produced on suitable substrata by most 

 species occurs usually in the form of a mat of discrete fructifications; 

 but in other species these fructi^cations are frequently combined 

 to form numerous and peculiar erect Isarioid sporodochia. 



4. In any case each individual fructification represents a well 

 characterized sporogenous apparatus, consisting of a sterile axial 

 filament bearing branches in an open racemose or dense capitate 

 arrangement. The primary branches may function directly as 



