196 THE AMERICAN MONTHLY [June 



mation in circular forms, viz., "immature at the centre, 

 mature at the periphery"; the growth of circular forms 

 being from the centre outwards. The climacosphenia 

 grows from the base or small end towards the apex or 

 wide end. 



The middle baud has coarse structure at the rate of 

 33,500 per inch. It" takes a fine 12 mm. apochromatic to 

 dot the outer and finer bands near the apex or large end 

 in a balsam mount, with axial cone illumination. When 

 this diatom is seen sideways it shows the interesting 

 structure alluded to above ; this consists of a helical pipe 

 passing through some bulkheads, which divide the diatom 

 into several compartments. As we come to the compart- 

 ments near the wide end, or older part of the valve, we 

 find that the pipe closes up and the bulkheads become 

 solid silex. 



Mr. Rousselet has appropriately suggested that this 

 structure is a useful test for 12 mm. apochromatics, and 

 similar objectives. With such glasses, however, the heli- 

 cal tube appears only like interlocking teeth, it requires 

 more aperture to develop its full beauty. — Q. Club. 



EDITORIAL. 



A Field of Labor. — Attention of microscopists is invi- 

 ted to the unsolved questions reg-arding alg-ae. What are 

 the changes that occur between the time when algae disap- 

 pear and reappear again ? Are not some algae mere stages 

 of growth of other algae, if so which ? Systematic obser- 

 vation during cultivation of such plants as Porphyridium 

 Oscillaria, Tetraspora, and Schizogonium are recommend- 

 ed. What are the life cycles of the marine algae, like 

 Laminarise, which can be cultivated from spores? 



Wanted. — B>arth containing diatoms from Redondo 

 Beach for a European Subscriber who offers cash, or, in 

 exchange, Hungarian diatomaceous material from St. Peter, 



