l886.J NEW-YORK MICROSCOPICAL SOCIETY. 157 



ellipse, constricted at the middle, is concerned with such layer- 

 groupings as are indicated by Figure i8. These singular nests 

 were very common, but I am not able to interpret them. Figure 

 2a is an arcuate form of uniform thickness and with obtuse or 

 rounded ends. There were many delicate rings, some broken, 

 but most of them whole. These were hoops, and indicated fre- 

 quent divisions, hence free propagation by the diatoms. 



Figure 3, a front view, is the normal type of an eccentric 

 group of asymmetrical forms, for from it have come all those 

 outre axydi capricious forms, represented by Figures 4 to 16, in- 

 clusive. There seems to be no limit to their diversity. The 

 figures represent but few of the large number of forms on the 

 one slide, which slide I exhibit here. Figure 4, a spatulate form, 

 shows the mildest or first aberrance from the type. Figure 5 

 suggests an alembic or retort, and so does Figure 6, which is 

 excessively and capriciously ornate. Figure 7 has begun to 

 divide, but the fission is on the wrong plane, being through the 

 side instead of the front. It is also jaggedly irregular. In 

 Figure 8, the division has stopped before going through the entire 

 length. Four valves are noticeable, and if the division were 

 normal and complete it would give two diatoms from the one in 

 the usual way ; but, not only is the division incomplete, it is also 

 abnormal. Normally, the two new diatoms would have, each, 

 one old or mother valve and one new or daughter valve, the 

 daughter valves being usually shorter than the mother valves ; 

 whereas, in Figure 8, the two inside valves, the daughter valves, 

 are, the one to the right disproportionately small, and the one to 

 the left large even to deformity. Figure 8% which, like 2^, is 

 drawn to half the scale of the others, has developed into a pinna 

 or mussel form and, thus being symmetrical, has made a com- 

 plete division ; still, the daughter valves are abnormal, being 

 longer than the mother valves. Figure 9, so like a club-foot in 

 appearance, is also dividing into similar monster forms. Figures 

 10, II, 12, and 13, each show in a different way abortive efforts 

 at propagating by division. Figure 14 has begun to divide, but 

 is itself a monstrous deformity. 15 and 16 are dumb-bell shaped, 

 double headed monsters in the act of dividing. The figure 

 which is at right angles to them and touching Figure 15, and 

 which differs so slightly from Figure 3, the initial form, seems to 

 be the normal of the abnormals 15 and 16. 



