28 American Quarterly Microscopical Journal. 



filament, were ovate .064 mm. long by .041 mm. broad, and 

 opened at one side near the top by a short, or, frequently, quite 

 long tube. (Figs. 6 and 7. PI. v). 



They required a much longer time to develop fruit than in 

 the first case. The zoospores were all distinct from each other 

 .009 mm. in diameter, and generally underwent a rejuvenes- 

 cence. The triton died in four days, but observations were 

 made until the plant ceased to grow, and no sexual fruit was 

 produced. Sep. 5th, a third triton was placed under the same 

 conditions as the second, and sown with fruit grown on the 

 second, the time of the appearance of the plant and its develop- 

 ment was nearly the same as in the former instance ; the new 

 sporangia however were produced as in the first forms described 

 (PI. V. Fig. i), and the late forms were the same as in the 

 former experiment, and in both cases the intestine had decayed 

 and broken away. The triton died in three days. Sep. loth, 

 the egg sac of a fourth triton was exposed and sown with 

 zoospores from the third experiment. The Saprolegnia de- 

 developed were the same as in the last case. In six days the 

 portion bearing the fungus was separated from the main part 

 of the ovary by the growth of a transparent membrane closing 

 the body cavity. Since then no filaments have appeared, and 

 now the triton seems to be in good condition for another oper- 

 ation. 



Although these experiments were not successful as far as the 

 production of oogonia is concerned, they are of considerable 

 importance as showing the great variability of the partheno- 

 genetir forms in different generations and different stages of 

 growth ; also the fact of their attacking healthy parts, although 

 in an unnatural condition, and causing their decay. 

 Concluded in our next issue. 



THE "OIL IMMERSION" OF CARL ZEISS COM- 

 PARED WITH THE OBJECTIVES OF 

 C. A. SPENCER & SONS. 



BY PROF. H. L. SMITH, LLD. 



Some four months ago I sent two objectives, by special 

 request, one to Belgium, the other to Germany. They were 

 made by C."A. Spencer & Sons, and were their then highest 



