A letter to 'The Times'

INDESTRUCTIBLE INFUSORIAL LIFE.

TO THE EDITOR OF THE TIMES.

Sir, The mysterious revivification of many of the minuter forms of infusorial life, notably rotifers, or as they are more commonly called wheel animalcules, cannot fail to surprise and interest those who may for the first time witness their evolution from a few small particles of earth and dust. A drop of water is sufficient to awaken from their longest sleep whole colonies of desiccated rotifers, will in a few minutes restore them to life and vigour and send them on their way rejoicing, just as their ancestors have gone in ages past.

Three years ago you did me the honour to insert in the columns of The Times a letter headed "A Curious Case of Evolution". In this letter I described a series of observations made under the microscope which seemed to show the indestructibility of those delicately and exquisitely organized animals, rotifers. To me it appeared that these wonderful infusorial animalcules enjoyed life all the more keenly for being subjected to a prolonged state of suspended animation, for on each occasion of revivification they 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, in as much as several members of the ciliata and tardigrada families have been included in them, and these have, although not to the same degree, exhibited a remarkable tenacity of life. I have likewise brought the intervals of sleep and vigorous life into strict accord with the durations 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 specimens 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 degrees (Fahrenheit), and subsequently the miniature aquarium in which they were enclosed was plunged into a freezing mixture. 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 standing higher in the scale of life were added to the water supplied to the rotifers, but in no way did they produce discomfort; on the contrary, portions were taken into the stomach and partly digested. On the other hand a drop of sewage water caused marked discomfort; they immediately retracted their rotating organs and sank down to the bottom of the cell. These were, so far as I can ascertain, poisoned, and this was probably owing to the free sulphide of hydrogen which my nose told me was being evolved by the putrescent sewage. 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 vulgaris, 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 observations 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 preponderate 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 resisting, as already pointed out, the extremes of heat, cold, and long-continued drought on desiccation, must excite a desire for a closer acquaintance with these monads, these curious specks of organization. So far as I can make out, the preservation of the rotifer under extraordinary circumstances is due to two special adaptations.

The outer integument of 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 longitudinal 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 insoluble envelope and secures it from further change.

Thus we are furnished with an example of organized matter which for months or years shows no evidence of life; indeed merely possessing a property which when acted upon by an appropriate agent gives rise to a series of actions which we recognize as life.

I remain, Sir, your obedient servant,

JABEZ HOGG.