298 



EVENINGS AT THE MICROSCOPE. 



DUMB-BELLS IN HOLOTHTJRIA. 



opposite end by two other dumb-bells ; and the structure 

 is complete as you see it. In almost all cases the two 



united globes of these ter- 

 minal elements are fused 

 into one globe, and in not 

 a few instances the ap- 

 pearance is as if these 

 two dumb-bells were but 

 one, bent over in a semi- 

 circular form ; but still a 

 good many specimens oc- 

 cur in which the two dumb-bells can be quite distinguished 

 from each other. The calcareous matter that solders the 

 elements together seems abundant, and has the appear- 

 ance that would be presented if they had been made of 

 solid glass, and united by glass in a state of fusion ; the 

 latter having apparently run together, so as to smooth and 

 round angles and fill up chinks, even where, as is often 

 the case, the globes themselves have only mutually ap- 

 proximated, and not come into actual contact. 



The average dimensions of these oval aggregations may 

 be .004 inch in length, and a little more than .002 in width; 

 but some specimens occur which are a little larger, and 

 others a little smaller than this ; while the irregular plates 

 are sometimes three times the length. 



Some of the more worm-like 

 members of this class have, 

 however, a skeleton composed 

 of pieces imbedded in their 

 skin, of even more remark- 

 able shapes than these. One 

 of these is the Chirodota 

 violacea — a native of the 

 southern coasts of Europe. 

 We have indeed a British 

 species of the same genus, a 



"WHEEL IN CHIRODOTA. 



