

which, it is supposed, presaged the echinoderms, 

 we infer that it was somewhat as follows: It was 

 a soft hyaline creature, totally without external 

 spines, plates or other hard parts, but possibly con- 

 tained a spicular skeleton. At the extreme forward 

 end was a sensory organ indicated by a cluster of 

 long cilia, perhaps the only seat of sensibility 

 through which it was enabled to apprehend the 

 outside world. Beside the probable paired water- 

 pores on its back, two other orifices were present: 

 the mouth, located underneath near the front; and 

 the vent, situated somewhere close to the rear- 

 ward end. It was devoid of external appendages 

 except for locomotor cilia which covered the entire 

 body. These cilia were shorter than the sensory 

 processes, and it was by the aid of their vibratory 

 movements that the animal swam. Indeed, it was 

 an unceasing swimmer, seldom, if ever, pausing to 

 rest; and it swam at, or very near, the surface of 

 the sea. But the arriving echinoderm is not yet; in 

 none of these structural features is represented the 

 peculiarities of the modern adult. 



Nevertheless, this anomalous creature was plas- 

 tic, so to speak; it was awaiting only some great 

 and influential factor to arise, causing an altera- 



[92] 



