456 C, CLIFl'^ORD DOBELL. 



investigation of tliese. The forms whicli I have studied most 

 carefully are those occurring in frogs and toads (Rana 

 teniporaria and Bufo vulgaris), in the common cockroach 

 (Stylopyga orien talis), and in Boa constrictor. It is 

 upon the organisms from the large intestine of this snake 

 that I have made the most complete series of observations, 

 and I will therefore record them in some detail at this point. 

 The living organisms, when removed from the host, and ex- 

 amined under an immersion, appear as large, bacterium-like. 



Text-fig. 



(iF' 







B 







Oo 



9o A 



^'''ij 



Bacterium-like organisms from large intestine of Boa con- 

 strictor. Living organisms. (Zeiss, 2"5 mm. apochromatic 

 water immersion X compens.-oc. 18.) 



non-motile rods (see Text-fig.). They may occur singly, in 

 pairs, or in chains. The average length of the largest in- 

 dividuals is about 14 /(. Smaller individuals are very common, 

 and many do not exceed 4/^. All intermediate sizes are to be 

 found. 



The rods all have rounded ends, and many of the longer in- 

 dividuals show a slight curvature (cf. Text-fig. b). The 

 internal structure in the living cells is very easily seen, though 

 the nucleus can be satisfactorily demonstrated in stained pre- 

 parations only. The cytoplasm is finely granular, and contains 

 as a rule a number of refractive bodies — probably reserve 



