ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 401 



the GloBocapsa fenestralis ; or very slender threads are produced, the 

 Leptoihrix parasitica Ktz. The identity of this form with Drilosiphon 

 has been fully established by the author ; instances are not infrequent 

 where a filament which is at the base a typical Drilosiphon terminates 

 at the upper end in a Leptothrix thread, then described as Leptoihrix 

 muralis Ktz. 



These leptothrix-hormogonia have a tendency to break up into 

 detached cells, some of which soon assume a rapid motion and partake 

 altogether of the nature of a vibrio. Others again agree altogether 

 with the structure and phenomena exhibited by Bacillus subtilis Cohn, 

 closing with the formation of spores and micrococci. The germination 

 of these has not been followed. 



Bacterial investigation of Sunlight, Gaslight, and the light of 

 Edison's Lamp,* — T. W. Engelmann continues his investigation of the 

 quality of different lights, as displayed by the difference in their effect 

 on the assimilating powers of bacteria. He finds that the relationship 

 between the assimilating effects of different wave-lengths of sunlight, 

 and the effect of corresponding wave-lengths of gaslight on green, 

 yellow, and blue-green cells of plants, is the same. The following 

 are given as the numbers for the assimilating effects at four different 

 spots of the prismatic spectrum of sunlight and gaslight respec- 

 tively: — 



(a.) With Green Cells. 

 BiO. D. Eih. F. 



Sunlight ., 100(61) 34-0(56) 13-9(44) 24-6(38) 



Gaslight ,. 100(208) 22-4(111) 5-6(105) 3-8(50) 



(6.) With Yellow Cells. 



BiC. D. Ei6. F. 



Sunlight .. 100(50) 55-1(47) 40-5(21) 40-4(7) 



Gaslight .. 100(196) 35-1(136) 15-5(65) 7-6(70) 



(c.) With Blue-green Cells. 

 Bi C. D. Ei 6. 



Sunlight .. 100(29) 75-4(32) 19-9(24) 



Gaslight .. 100(113) 50*7(99) 7-6(49) 



The figures between brackets denote the number of measurements, 

 from the average of which the numbers are derived. 



If from these numbers the relative assimilating energy of gaslight 

 is calculated in a percentage of the energy of the corresponding wave- 

 lengths of sunlight, the two energies being taken as equal in B^ C, the 

 following results are obtained : — 



With green cells ; 65 • 9 per cent, at D ; 40-4 per cent, at E| 6 ; 19-5 per cent, at F. 

 „ yellow „ 63-7 „ 38-3 „ 18-8 „ 



blue-) 68-8 „ 38-2 



" green/ " ' 



The coincidence between the corresponding numbers in these 

 three rows is so great that, reckoning possible sources of error, they 

 * K. Akad. Wetensch. Amsterdam, Nov. 25, 1882. See Bot. Centralbl., xiii. 

 (1883) p. 214. 



Ser. 2.— Vol. III. 2 D 



