182 



in balsam or styrax. Stained Bacteria and Micro- 

 cocci. 



Test Plate.- -This will be an excellent acqui- 

 sition for all those who can meet the pecuniary 

 outlay. It consists of a series of 20 diatoms ar- 

 ranged according- to the coarseness of the lines. 

 They are furnished mounted both in balsam and 

 styrax. Below is a table giving the numbers, 

 names of the various diatoms and divisions on 

 their surfaces to yoVo m ch. A specimen of Eupo- 

 discus argus begins and ends the series : 



Stiriffi in Tl ^ 

 inch. 



1. Triceratium favus, Ehrbg., - 3.1 to 4. 



2. Pinnularia nobilis, Ehrbg., 11.7 to 14. 



3. Navicula lyra, Ehrbg. var., 14.5 to 18. 



4. Navicula lyra, Ehrbg., 23. to 30.5 



5. Pinnularia interrupta, Sm. var., 25.5 to 29.5 



6. Stauroneis phoenicenteron, Ehrbg., 31. to 36.5 



7. Grammatophora marina, Sm., - 36. to 39. 



8. Pleurosigma balticum, Sm., 32. to 37. 



9. Pleurosigma acuminatum (Kg.) 



Grun., - 41. to 46.5 



10. Nitzschia amphioxys, Sm., 43. to 49. 



11. Pleurosigma angulatum, Sm., 44. to 49. 



12. Grammatophora oceanica, Ehrbg. 



G. subtilissima, 60. to 67. 



13. Surirella gemma, Ehrbg., 43. to 54. 



14. Nitschia sigmoidea, Sm., 61. to 64. 



15. Pleurosigma fasciola, Sm. var., 55. to 58. 



