52 A Guide to the Zoological Collections in the 



shown (enlarged) in fig. 3, by a continual snapping action 

 seize and hold the animalcules that form the prey of the 

 colony. Others become transformed into long lashlike 

 filaments, known as vibracula (fig. 4), which also serve 

 the colony by sweeping prey into the mouths of the ordi- 

 nary zooids. 



The Polysoa of the Indian Seas have not as yet been 

 systematically investigated. Many of them appear to be 

 identical with well-known European forms, a fact that is 

 easily explained when it is remembered that Polyzoahahi' 

 tually encrust the bottoms of ships, and are thus likely to 

 be widely distributed along frequented lines of navigation. 



In the exhibited collection of Indian Polyzoa specimens 

 of the following genera are included : — Cellularia, Rete- 

 pora, and Cellepora. 



As already stated, the majority of the Polyzoa are 

 marine. They incrust rocks, dead coral, etc., and thus 

 contribute considerably to the growth of reefs. They also 

 incrust all sorts of floating drift. The larvae are free-swim- 

 ming. 



PHYLUM IV OF THE CCELOMATA. 



ARTHROPODA. 



[(Ea0£0 37—42 nlong <i;orlhertt toali, 48—63 alotts acsUrn 

 toaU, 64—69 along Southern toali, aitl) ^^©k-ras^s 

 70-125]. 

 The great phylum of the Arthropoda includes the re- 

 markable form Peripatus^ the Myriapoda (Centipedes), 

 the Hexapoda (Insects), the Crust acea,2.Vi^ the Arachnida 

 (Spiders and Scorpions). It contains an immense number 

 of species, far more in short than all the species of all 

 the other phyla put together. 



In their general plan of structure the Arthropoda re- 

 semble the Annelida proper, and the main groups of the 



