104 



THE AMERICAN MONTHLY 



[June, 



hairs. As the insect is quite active 

 it must be that this fringing of the 

 tiny eyelets with liair does not mate- 

 rially obscure its vision. When the 

 minuteness of this singular arrange- 

 ment is considei'ed, it is surely re- 

 markable. This general hairiness of 

 the female especially, and that about 

 the head, neck, and forward part of 

 the thorax, stands correlated to a beau- 

 tiful structure found only in the male, 

 which has on the tarsus of each leg in 

 the forward pair what the lecturer 

 called a sexual coinb. It is a beauti- 

 ful comb of a very dark brown color, 

 each comb having ten pointed and 

 strong teeth. In the nuptial embrace 

 these combs are fixed in the hairy 

 front of the thorax of the female, 

 thus becoming little grapnels. 



The flies love any vegetable sub- 

 stance in fermentation, whether acetic 

 or vinous. Hence it will abound 

 about cider mills, swarm on preserves 

 in the pantry, and in cellars or places 

 where wine is being made or stored. 

 The paper showed the tendency of 

 the glucose in the over-ripe grape to 

 the vinous ferment, and that the fly 

 delighted in it. A singular accident 

 showed how they loved even the very 

 high spirits. In making some of the 

 mounts shown to the society Dr. 

 Lockwood had left a bottle of 90 per 

 cent, alcohol uncorked over night. 

 Next morning he was astonished to 

 find his alcohol of a beautiful ame- 

 thystine color, and the cork out. In- 

 spection showed a number of these 

 tiny creatures w^hich, when filled with 

 the purple juice of the grape, had 

 smelt the alcohol in the open bottle, 

 and had gone in to drink. They had 

 ignominiously perished, and had given 

 color to the liquid. 



Structure of the Diatom-shell. — 

 IT. 



BY JACOB D. COX, LL. D., F. R. M. S., 

 PRES. AM. SOC. OF MICR. 



In studying the naviculte we begin 

 with the large Pmnularia^ where the 

 size of the valves and the simplicity 



of the marking make easy the appli- 

 cation of the criteria we have already 

 established. Using transmitted light, 

 the raphe is found to show the color 

 of the general background, whilst the 

 smooth longitudinal portion of the 

 valve next it is tinted with the pink 

 color which indicates thickening of 

 the silex. The central nodule shows 

 this in a higher degree, with lenticu- 

 lar effects. The costae are pink in 

 tint also, and in large specimens of 

 P. major the interspaces between the 

 ribs are often divided into what ap- 

 pear to be two large oval depressions, 

 of which that next the midrib is the 

 shallower, as is shown by its excess 

 of color over the outer one. The 

 central nodule often extends consid- 

 erably beyond the inner end of the 

 median line, which is a little enlarged, 

 and seems to terminate in a circular 

 dot, which, by its bright light and 

 freedom from color, should be a de- 

 pression reaching nearly or quite 

 through the nodule. In a specimen 

 of P. alpina from a Scotch gathering 

 I have found a valve turned partly on 

 one side, so as to give an obliquely 

 transverse view through the valve, and 

 in this the enlargement of the median 

 line is plainly seen to extend like a 

 tube through the thick prolongation 

 of the central nodule. It is not un- 

 common to find broken valves oi Pin- 

 nulai'ia in which the costas project 

 boldly beyond the interspaces of which 

 the thin film has been partly broken 

 away. I have noted a specimen of 

 P. divergens in which the thin film 

 has been almost wholly removed by 

 some accidental grinding process, and 

 the costae stand out along each side 

 like the teeth of a comb. Prof. H. 

 L. Smith has given me another simi- 

 lar example of P. major. The raphe 

 appears to be a channel having a 

 ver}^ thin film at the bottom, which 

 is part of the firm silex on one side, 

 and laps under the other side in a way 

 similar to the ' rabbet' in joinery. 



Of the dotted naviculse, N. lyra 

 may fairly be taken as the type. Its 

 beautiful regularity of form and the 



