^6 



THE AMEHICAN MONTHLY 



[February, 



exquisitely organized animals, roti- 

 fers. To me it appeared that these 

 wonderful infusorial animalcules en- 

 joyed life all the more keenly for be- 

 ing subjected to a prolonged state of 

 suspended animation, for on each oc- 

 casion of revivification the}' instantly 

 resumed their functional activity all 

 the more eagerly, and precisely at the 

 point where it was so rudely broken 

 off or interrupted. My experiments, 

 now extending without a break over 

 a third year, have been slightly varied 

 from those of previous years, inas- 

 much as several members of the Cili- 

 ata and Tardigi'ada families have been 

 included in them, and these have, 

 although not to the same degree, ex- 

 hibited a remarkable tenacity of life. 

 I have likewise brought the intervals 

 of sleep and vigorous life into strict ac- 

 cord with the diu'ations of dry and wet 

 periods of the year, so that my pets have 

 been kept in a perfectly dry condition 

 during the whole of the long drought 

 which characterized the past summer. 

 Moreover, some older dried speci- 

 mens were subjected to an artificial 

 process of desiccation. They were 

 kept for a time in a hot-air chamber, 

 the heat in which was raised to 200° 

 F., and subsequently the miniature 

 aquarium in which they were inclosed 

 was plunged into a freezing mix- 

 ture. Neither process killed them 

 nor greatly diminished their vital 

 powers, their revivification in both 

 cases being somewhat delayed. 



Certain toxic agents known to exert 

 a baneful influence over animals stand- 

 ing higher in the scale of life were 

 added to the water supplied to the 

 rotifers, but in no way did they pro- j 

 duce discomfort ; on the contrary, \ 

 portions were taken into the stomach ! 

 and partly digested. On the other t 

 hand, a drop of sewage water caused 

 marked discomfort ; they immedi- 

 ately retracted their rotating organs 

 and sank down to the bottom of the 

 cell. These were, so far as I can as- 

 certain, poisoned, and this was prob- 

 ably owing to the free sulphide of 

 hydrogen which my nose told me was 



being evolved by the putrescent sew- 

 age. I lay more stress on this fact 

 because it is said that these and other 

 forms of infusorial life live and thrive 

 in stagnant water. Nothing of the 

 kind : they require a free supply of 

 oxygen, as do other aquatic animals. 

 The wheel-like organs surmounting 

 the elongated body of Rotifer vulga- 

 ris^ and which are seen constantly in 

 motion when the animal is in health, 

 have a treble task assigned to them — 

 that of furnishing a supply of food, 

 renewing the fresh air, and assisting 

 in locomotion. From my observa- 

 tions I am led to infer that rotifers 

 will live and multiply on a very scanty 

 supply of organic matter, provided 

 only that the water is fairly well 

 oxygenated. One other noteworthy 

 change I ought to mention, the greatly 

 diminished or no longer developed 

 eye, due, no doubt, to the withdrawal 

 of the stimulus of light, my rotifers 

 being nearly always kept in the dark. 

 Of the sexes, the females greatly pre- 

 ponderate over males. 



In some considerable colonies not a 

 male can be seen. The remarkable 

 power the rotatoria and some few 

 other infusorial families have of re- 

 sisting, as already pointed out, the 

 extremes of heat, cold, and long-con- 

 tinued drought on desiccation, must 

 excite a desire for a closer acquaint- 

 ance with these monads, these curi- 

 ous specks of organization. 



So far as I can make out, the preser- 

 vation of the rotifer under ordinary 

 circumstances is due to two especial 

 adaptations. The outer integument 

 or skin, although composed of a firm 

 material, is divided, like a coat of 

 mail, into four or five segments ; these 

 are under the control of a set of longi- 

 tudinal muscles, which, when called 

 into action, enable the little creature 

 to shut itself up, telescopic fashion, 

 and, sinking down, it assumes an 

 ovoid form. As the water in the cell 

 dries up a secreting organ is brought 

 into play, and exuding a gelatinous 

 kind of fluid, covers it with an in- 

 soluble envelope, and secures it from 



