1889.] NATURAL, SCIENCES OF PHILADELPHIA. 139 



caenobium impelled by the flagella of its cells projecting through its 

 envelope of cellulose. The direction of the rotation of the eaenobia 

 is not constant and may be either sinistral or dextral, but the 

 direction of progress always coincides with an imaginary axis pass- 

 ing through the centre of the anterior empty pole and the posterior 

 germ-bearing portion of the nearly spherical colony or caenobium. 

 These poles are sometimes differentiated before the young Yolvoces 

 leave their parent caenobium, which they do by breaking through 

 the wall of the latter at its hinder pole. 



The diameter of a Volvox caenobium is slightly longer measured 

 along the axis around which it revolves than in the direction trans- 

 verse to it. It results from this that the eaenobia are somewhat 

 smaller equatorially than axially so that the form of the whole is 

 that of a very slightly oblong spheroid. These characters are fairly 

 constant and nearly always apparent while that of the production of 

 the spore in a little more than the posterior hemisphere of the 

 caenobium is invariable as well as the uniform direction of the axis of 

 progressive locomotion in relation thereto. 



Another very extraordinary fact which was observed was that 

 the so-called " eye-spots " found in the flagellate cells of the anterior 

 pole of the spherical caenobium were the largest, and invariably 

 occupied a definite position with relation to the flagella and to the 

 axis around which the colony rotated. The anterior cells had the 

 brownish red " eye-spots " largest, and as one examined row after row 

 of the cells of the caenobium in succession backward toward what 

 one might term the caudal pole these "eye-spots" were seen to 

 gradually diminish in size, until in the last cells of the hinder pole, 

 they were barely distinguishable as minute reddish points, which 

 elevated the protoplasm of the cells into a slight prominence, such 

 as is more marked over the larger anterior '■ eye-spots. " This re- 

 markable fact of the " eye-spots " of the anterior pole being the 

 largest, revives in a striking way the query whether these reddish 

 bodies are not really visual organs or sense organs of some kind, 

 after all, as originally supposed by Ehrenberg. Their gradual 

 diminution in size toward the posterior pole where they are nearly 

 atrophied would seem to indicate that they were in some way 

 related to the power of the organism to move in a definite direction, 

 the cells of the anterior end being provided with the best developed 

 visual, sensory apparatus, or whatever it may be. If it should 

 prove possible to show that these "eye-spots" are really sensory 

 organs in Volvox, as all the facts which have been here noted would 

 seem to indicate, it would be one of the few instances known of a 

 plant possessed of visual or sensory organs of any kind unless we 

 except some such plants as the Venus' fly-trap. 



The speaker stated that he had been unable to find any notice of 

 any of the features of Volvox, which are here described ; all of the 

 figures to which he had had access in standard works were entirely 

 erroneous from their authors having completely overlooked these 



