481 



cesses, that is, all such as are accomplished with time- regulated 

 alternations, whether of motion or any other change. 



Probably; the simplest example of rhythmic motions yet known 

 is that detected by the acute researches of Professor Busk* in the 

 Volvox globator. At a certain period of the development of this 

 simplest vegetable organism, there appear, in each zoospore, or in 

 the bands of protoplasm with which the zoospores are connected, 

 vacuoles, spaces, or cavities, of about g-^oth ^ an inch i diameter, 

 which contract with regular rhythm at intervals of from 38 to 41 

 seconds, quickly contracting and then more slowly dilating again. 



The observations of Cohnf, published about a year later than 

 those of Mr. Busk, but independent of them, discovered similar 

 phenomena in Gonium pectorale and in Chlamydomonas, the vacuoles, 

 like water-vesicles, contracting regularly at intervals of 40 to 45 

 seconds. The contractions and the dilatations occupy equal periods, 

 as do those of our own heart- ventricles ; and in Gonium he has found 

 this singular fact, that when, as commonly happens, two vacuoles 

 exist in one cell, their rhythms are alike and exactly alternate, each 

 contracting once in about 40 seconds, and the contraction of each 

 occurring at exactly mid-distance between two successive contractions 

 of the other. 



Here, then, we have examples of perfect, and even of compound, 

 rhythmic contractions in vegetable organisms, in which we can have 

 no suspicion of muscular structure, or nervous, or of stimulus (in 

 any reasonable sense of the term), or, in short, of any one of those 

 things which we are prone to regard as the mainsprings of rhythmic 

 action in the heart. 



The case of ciliary movements is as simple ; the cilia having a 

 perfect rhythm, so that their alternate and opposite movements are 

 of definitely proportioned length ; and that, where many move on 

 the same surface, they all keep time precisely, by moving, not all 

 simultaneously, but in time-regulated succession. Here, too, we 

 have no trace of muscular or nervous structure, or of stimulus ; yet 

 there is a perfect rhythm in which even myriads of cilia keep time, 



* Transactions of the Microscopical Society of London, May 21, 1852. 

 t Untersuchungen iiber die Entwickelungsgeschichte der mikroskopischen 

 Algen und Pilze. Breslau, 4to, 1854. 



