68 INTRODUCTION TO ZOOLOGY. 



luminosity of the Annelid may be formed, by supposing its 

 body to be represented by the slit in a silver spangle, and its 

 luminosity by the disc of the spangle."* 



Some among these creatures occasionally present themselves 

 to our notice in situations where they would be least expected. 

 Thus, Templeton describes one (Spio calcarea) "living in 

 minute tubular cavities, in our limestone rocks, the tentacula 

 alone projecting, and kept by the animal in constant motion."f 

 We have noticed the same, or some allied species, in rock 

 pools on the County Down coast, where there is no limestone. 

 There the pinkish substance, now regarded as vegetable, J 

 that lined the pools, formed the materials of its dwelling, and 

 the minute waving tentacula gave animation and interest to 

 the otherwise quiet little basins. 



CLASS II CIERIPEDA. 



BARNACLES AND ACORN-SHELLS. 



" There are found in the north parts of Scotland and the islands ad- 

 jacent, called Orchades, certain trees, whereon do grow certain shells of 

 a white colour, tending to russet, wherein are contained little living 

 creatures ; which shells in time of maturity do open, and out of them 

 grow those little living things, which, falling into the water, do become 

 fowls which we call Barnacles." 



THE words which we have selected as the motto for the pre- 

 sent chapter occur in Gerardcs' " Herbal, or General History 

 of Plants," a work published in 1597, and regarded for more 

 than a century afterwards as one of the best sources of 

 botanical information. Its author resided in Holborn, and 

 established there a " physic garden" of his own, which was 

 probably, at that period, the best of its kind in England for 

 the number and variety of its productions. The transformation 

 above mentioned he gives on the authority of others. " Thus 



* As all our readers may not be familiar with the ornament to 

 I which our friend, Mr. Ball, has referred, we annex a wood-cut, 



which will render his illustration more perfectly understood, 

 f Mag. Nat. Hist. vol. ix. page 233. 

 J Millepora polymorpha. 



