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THE POPULAR SCIENCE MONTHLY 



the somatic flow is observed the like cause may account for the like 

 eifect. 



The exquisite colors of the hydroids, which rival the tints of our 

 loveliest flowers, are due to the colored granules secreted by the ani- 

 mal and discharged into the somatic fluid. A charm is added to these 

 flowers of the sea l)y the flashing opalescent gleams of color which 

 shine out from their crystalline walls. Even the exquisite representa- 

 tions of Allman, in his monograph on " The Tubularian Hydroids," fail 

 to give an idea of the beauty of form and color to be found in the real 

 object. The Hydra viricUs is so called from its brilliant green color. 

 This green is said by Allman to be of the nature of chlorophyll, and 

 to possess the power, like the chlorophyll of plants, of decomposing 

 carbonic acid, assimilating the carbon, and yielding up the oxygen. 

 If this be true (and there is no reason to doubt it, Allman being one 

 of the highest authorities), it only furnishes, in this form of animal life, 

 one more curious resemblance to vegetation, and denies one more 

 tradition of its animality. 



Fig. 8. Sertularina cupressina. (Magnified.) 



The most singular facts in connection with hydroid life lie in the 

 vai-iety of its modes of reproduction. It would almost seem as though 

 every form of reproduction known in Nature had been mutely proph- 

 esied in the primeval world when the fossil hydroid and trilobite lived 

 side by side in the Silurian seas. 



They are generated, like plants, by buds and by artificial sections ; 

 like plants, they are able, from a small fragment, to produce the whole 

 organism. They, however, go farther than most plants in this power 

 of reproducing lost parts ; for a small fi-agment taken from any por- 



