ZOOPHYTES OF GUERNSEY. 169 



intervals slowly over the surface of the poljp-cell, and removes 

 whatever might be injurious to the delicate little tenant that 

 inhabits it. 



Two modes of reproduction are met with in the Polyzoa, 

 — sexual and asexual. The former takes place by means of 

 ova, the latter by the simple process of gemmation, or budding. 

 The young forms or larvae which are developed from the ova 

 are free-swimming, and constantly in motion ; in many 

 instances they are remarkable by the singularity and beauty 

 of their shapes and colours. After enjoying a brief period of 

 activity, the larval form attaches itself to some object, and 

 imdergoes a change ; and then develops into the primary cell 

 Avhich forms the nucleus of the future colony. 



The young zoologist who is looking about for fresh fields 

 for observation and study, will find none more promising than 

 the reproduction and embrvology of the Polyzoa, about which 

 a vast deal has still to be learnt ; and no finer area for research 

 exists anywhere in the world than the shores of Guernsey and 

 the neio-hbourino^ islands. 



In common with many other microscopic inhabitants of 

 the ocean, both the groups we are now considering contribute 

 very largely, during their early stages as mr^dusiform zooids 

 or larvae, to the wonderful and very beautiful phenomenon 

 known as " the phosphorescence of the sea." But the lumi- 

 nosity is not confined to the immature stages ; it resides in 

 the adult polyps as well ; as may be proved by gently agitating 

 the water of the aquarium in which they are kept alive, when 

 the little creatures will be seen to glitter in the dark like 

 myriads of diamonds. In some of the common species every 

 tiny cell beams with a point of light like a brilliant star, so 

 that the entire colony has been aptly compared to an illumin- 

 ated city in miniature. 



Anyone who begins to study the living zoophytes on the 

 seashore will soon discover a curious circumstance in connec- 

 tion with their mode of life ; namely, that certain species 

 affect certain habitats, and are very rarely, or perhaps never 

 found elsewhere. Some grow only on one particular kind of 

 seaweed, or on one kind of shell or stone. There would be 

 nothing strange in this if they were true parasites ; but since 

 they derive no nourishment whatever through the root, as 

 plants do, it is a matter for speculation why one sort of base 

 should be more favourable for growth than another. It would 

 seem to indicate some power of selection, or at any rate some 

 advantage to be derived for the welfare of the colony ; for it 

 may be that the young of all species attach themselves indis- 



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