POLYZOA. 411 



existence which so many of their contemporaries have had to 

 endure daring the long aeons of time which have elapsed since 

 they first became dwellers in the early Primary seas, we need not 

 be surprised to find them at the present day so comparatively 

 little'altered in structural character from what they were in those 

 far-off Silurian times. Their history is, in truth, an ancient one. 

 There are few existing forms which can be so accurately traced 

 through these immense geological periods and still be found 

 flourishing in pristine glory in so many of the seas and waters of 

 this globe. The Darwinist may, with good reason, maintain that 

 the small amount of variation and development which this very 

 ancient family has undergone in no way disproves the teaching of 

 his great master, Charles Darwin. The sentences I have quoted 

 from that masterly work, "The Origin of Species," make it plain 

 that Darwin's theory satisfactorily accounts for such seeming 

 anomalies as the history of the Polyzoa presents. 



Thoughts like these bring to my mind the words : — 



" Flower in the crannied wall, 

 I pluck you out of the crannies ; 

 Hold you there, root and all in my hand, 

 Little flower; but if I could understand 

 What you are, root and all, and all in all, 

 I should know what God and man is." 



EXPLANATION OF PLATES XVIIL, XIX. 



Fig. 1. — Fludra foliacea, one of the Sea-mats, a, Portion of the 

 colony, natural size ; 6, A fragment magnified to show the 

 cells in which the separate polypicles are contained. After 

 Nicholson. 



,, 2. — Diagram of a Polyzoon (after Allman). a, Region of the 

 mouth, surrounded by tentacles ; b, Alimentary canal ; 

 c, Anus ; d, Nervous ganglion ; e, Investing sac (ectocyst) ; 

 /, Testis. 



3. —Bird's head process, or " avicularium " of a polyzoon (mag- 

 nified), after Allman. 



4. — Polyzoa, Silurian period. Builders' Beds, Wenloch Shales. 



5. — Polyzoa, Carboniferous period. Coal Shales, Scotland (greatly 

 enlarged). 



6. — Recent Polyzoa, Bay of Naples. 



Drawn by W. G. Wheatcroft. 



n 



5 > 



5) 



n 



