400 Dr. E. W. A. Walker. [May 16, 



6. Later stage of division ; the chromatin-spheres are massed oil the thread joining 



the blepharoplasts. 



7. The chromatin-niasses have passed to either pole of the dividing monad ; the line 



joining the blepharoplasts still persists. 



8. Division is almost complete, and the line between the blepharoplasts has dis- 



appeared. 



9. One of the products of a recent division ; the nucleus has not yet been recon- 



structed. 



10. Early stage of conjugation. 



11. Active zygote-stage showing the approximation of the blepharoplasts and large 



vacuoles. 



12. Early stage of encystation of the zygote ; the wall at this stage is quite soft and 



stains with eosin. 



13. Unripe cyst, showing reserve-body. Iron-h;Tematoxylin preparation. 



14. Unripe cyst, showing possibly reduction-division on the part of the nuclei. 



15. Almost ripe zygote cyst, with elongated synkaryon. Hamialuni-preparation ; does 



not show reserve-body. 



16. Eipe cyst, with round synkaryon. Hjemalum-preparation ; does not show reserve- 



body. 



Further Observations on the Variability of Streptococci in Relation 

 to Certain Fermentation Tests, together with some Considera- 

 tions Bearing on its Possible Meaning. 

 By E. W. Ainley Walker, M.A., D.M., Fellow and Tutor of University 

 College, and Lecturer in Pathology in the University of Oxford. 



(Communicated by Prof. Gotch, F.R.S. Received May 16,— Eead 

 June 20, 1912.) 



(From the Department of Pathology, University of Oxford.) 



The fermentation tests devised by Mr. H. Gordon (1905, 1) were employed 

 by him and by a number of subsequent observers as a means of differentiating 

 streptococci into definite varieties. 



This application of the tests necessarily presupposes the stability of the 

 reactions yielded by any given strain of streptococci in the test media. 

 But after a prolonged examination of a number of different strains of 

 streptococci I was unable to confirm this primary requirement. Con- 

 sequently, 1 ventured to call in question the supposed constancy of the 

 tests (1910,2; 1911, 3). A considerable mass of evidence of the variability 

 of streptococci under cultivation in respect of their reactions in " Gordon's 

 media " was submitted. The observations recorded made it clear that the 



