THE RELATIONS OF PROTOZOA TO MOLLUSCA. 243 



what obtains in Protozoa; in the latter the plane of the axis is 

 rolled in a spiral, whereas in the Zoophytes the plane is fixed 

 and the spiral winds around it. 



Among all the other forms of Zoophytes there are none, neither 

 among Polyps nor Starfishes, of which it could be urged, with 

 the faintest show of reason, that they are related to Protozoa. 

 Hydra, and its congeners, although the best and most favorable 

 instances of relationship to Protozoa, failing to hold what is 

 claimed for them, the rest of the Zoophytes are of course out of 

 the question. 



Protozoa and Mollusca. We will pass now to the considera- 

 tion of the alleged relations of the Vorticellae (one of the several 

 groups among Protozoa] to Mollusca. As long ago as 1846, 

 Van der Ho3ven, a Hollandish naturalist, suggested the rela- 

 tionship of the Vorticellse to Mollusca, saying that " probably 

 one day they will be ranked among Bryozoa." The latter is one 

 of the lowest groups of Mollusca. Since that time others have 

 repeated his suggestion. It is my task now to ascertain what 

 amount of truth there may be in the Hollandish naturalist's 

 prophecy. As I have already described and recapitulated (p. 

 160-176) the structure of the Protozoa, I need only refer to that 

 group whilst I proceed to take in hand the Bryozoans. 



The remarkable symmetry of the various constituents of their 

 organization, which I have spoken of on a former occasion, (p. 

 195,) will be recalled to your minds by reference to these figures, 

 (figs. 118, 119, 120, Pectinatella and Fredericella) ; and therefore 

 I need not enter into any details in regard to that point.* What 

 is most likely to attract your attention, in the comparison of the 

 two groups, is the distinctness of the stomach (st) and intestine 

 (cl to an) of the Bryozoa from the rest of the body, and the 

 equally free play allowed to the muscles, (r, r 1 ,) to say but a 

 word in regard to the distinctness and especially assigned posi- 

 tion of the nervous ganglion (). When, therefore, we analyze 

 the impression which we receive from the contemplation of these 

 two groups, e. g-., Vorticellge (fig. 95) and Bryozoa (figs. 118, 



* The symmetry of the young Bryozoan, and the peculiarity of the type to 



