116 F. W. PHILLIPS OBSEEVATIONS ON EOTIFERS. 



be undescribed, but subsequent investigations have convinced me 

 that tliey were males, and I have regretted that I did not give 

 more time to tracing their career. Those who advocate " Women's 

 Rights " may perhaps be gratified to learn that the male is 

 undoubtedly the inferior sex. It is a curious fact that the males 

 are always smaller than the females, and that the digestive 

 apparatus is entirely absent; they are consequently short-lived, 

 generally dying within a few hours after their birth. The female 

 produces two kinds of eggs. The summer eggs, which are quickly 

 hatched, and the winter eggs, which are preserved against the cold 

 by a peculiar shell until they are hatched in the following spring. 

 It is remarkable that each batch of eggs are either all female, or all 

 male, the latter being about one-third the size of the former. The 

 Rotifera illustrate the theory of Parthenogenesis. The rapidity with 

 which they multiply and develope is truly wonderful. The Hyda- 

 tma, for instance, lays about four eggs a day ; the eggs are extruded 

 within a few hours from the time in which the rudiments are first 

 visible within the ovary, and within twelve hours after this the 

 shell bursts and the yoimg rotifers come forth. These young ones, 

 when two days old, lay a like number of eggs. Professor Eliren- 

 berg calculated that sixteen millions may be produced within 

 twelve days from one single female ; there is, however, an error in 

 his calculations ; it should be nearly seventeen millions within 

 twenty-four days. 



An account of the Rotifera would be incomplete if I were to omit 

 to mention one remarkable fact in connection with them, and that 

 is their power of revivification after being dried up. They may be 

 exposed to the heat of a broiling sun, or placed in the exhausted 

 receiver of an air-pump, heated gradually up to 200° Fahr., and 

 reduced to such a state of brittleness that they break when touched 

 with a needle, yet, when moistened, they will speedily revive. 

 Taking advantage of this property, microscopists sometimes keep 

 by them stocks of desiccated rotifers. According to Mr. Slack, the 

 Rotifera, when drying, give off a slimy secretion that forms an im- 

 pervious casing which prevents them from being entirely dried up. 

 When they are heated too much or too suddenly, they lose their 

 vitality. Taking these facts into consideration, it is not so difiicult 

 to account for their sudden appearance in unexpected places. We 

 can readily comprehend how they are borne upon the wind and 

 scattered broadcast upon the meadows, the ditches, and the 

 housetops. 



The Rotifera are easily procured ; there is scarcely a ditch, pond, 

 or puddle in which some members of this family may not be found ; 

 indeed they are not entirely confined to fresh Avater, some few 

 species being found in the sea. 



Rotifer vulgaris has often been found in the cells of bog-moss 

 {Sphagnum), and Alhertia vermicular is is found parasitic within the 

 intestines of earthworms and slugs. The habitat, however, in 

 which they may be looked for with most success is in accumulations 

 of standing water which are tolerably free from decomposing 



