TEE GROUND BETWEEN ANIMALS AND PLANTS. 649 



great activity, with a curious rolling motion, by the lashing of the 

 front cilium, while the second cilium trailed behind ; sometimes it 

 anchored itself by the hinder cilium and was spun round by the work- 

 ing of the other, its motions resembling those of an anchor-buoy in a 

 heavy sea. Sometimes, when two were in full career toward one an- 

 other, each would appear dexterously to get out of the other's way ; 

 sometimes a crowd would assemble and jostle one another, with as 

 much semblance of individual effort as a spectator on the Grands 

 Mulets might observe with a telescope among the specks representing 

 men in the valley of Chamounix. 



The spectacle, though always surprising, was not new to me. So 

 my reply to the question put to me was, that these organisms were 

 what biologists call Monads, and though they might be animals, it 

 was also possible that they might, like the Bacteria, be plants. My 

 friend received my verdict Avith an expression which sliowed a sad 

 want of respect for authority. He would as soon believe that a sheep 

 was a plant. Naturally piqued by this want of faith, I have thought 

 a good deal over the matter; and as I still rest in the lame conclusion 

 I originally expressed, and must even now confess that I cannot cer- 

 tainly say whether this creature is an animal or a plant, I think it may 

 be well to state the grounds of my hesitation at length. But, in the 

 first place, in order that I may conveniently distinguish this "monad " 

 from the multitude of other things which go by the same designation, 

 I must give it a name of its own. I think (though, for reasons which 

 need not be stated at present, I am not quite sure) that it is identical 

 with the species Monas lens, as defined by the eminent French micro- 

 scopist Dujardin, though his magnifying power was probably insuffi- 

 cient to enable him to see that it is curiously like a much larger form 

 of monad which he has named ^eierow^^Ya. I shall, therefore, call it 

 not 3Ionas, but Heteromita lens. 



I have been unable to devote to my Heteromita the prolonged 

 study needful to work out its whole history, which would involve 

 weeks, or it may be months, of unremitting attention. But I the less 

 regret this circumstance, as some remarkable observations, recently 

 published by Messrs. Dallinger and Drysdale,* on certain monads, 

 relate, in part, to a form so similar to my Heteromita lens, that the 

 history of the one may be used to illustrate that of the other. These 

 most patient and painstaking observers, who employed the highest 

 attainable powers of the microscope and, relieving one another, kept 

 watch day and night over the same individual monads, have been en- 

 abled to trace out the whole history of their Heteromita ; which they 

 found in infusions of the heads of fishes of the cod tribe. 



Of the four monads described and figured by these investigators, 



' " Researches in the Life-history of a Cercomonad : a Lesson in Biogenesis," and 

 " Further Researches in the Life-history of the Monads," Monthly Microscopical Journal, 

 1813. 



