' 



KNOWLEDGE. 



May, UJ15. 



Figure 127. Transverse section of the spine o) Cidaris, 

 taken witb a one-inch objective. X 70. Exposuie 4 mins. 



Figure 129. Arachnoidiscus Ehrenbergii, taken with 

 a half-inch objective. X 280. Exposure 6 mins. 





FIGURE 12S. Transverse section of the spine of Echinus, 



taken with a two-third inch objective. X 60. Exposure 



3£ mins. 



Figure 130. Hcliopcita Metii, taken with a half-inch 



objective. X400. Exposure 8 mins. 



From photomicrographs by A, Wellesley-H arris, M R C S . 

 And illustrating his papei on "Some Hint-, on Pboto-micrography " in The Journal of the Photo-micrographic Society. 



In all cases, projection ocular No. 4 was used; the illuminant «as incandescent gas and the filter, anramine 



(see page 153). 



