I nvertehrate Gnllcry of the Indian Museum. 



productive. For example, in the Millepora, as is shown in 

 the enlarged drawings after Moseley, the colony consists of 

 a multitude of polyp-like zooids bound together by a hard 

 stone-like ccenenchyma, as is seen in the exhibited speci- 

 men. The zooids are grouped together in little groups of 

 six, in each of which the central zooid is short and stout 

 with a mouth and few tentacles, while the five peripheral 

 zooids are long and thin and flexible, and have no mouth 

 but numerous tentacles. The central zooid, or gastrozooid, 

 is specially modified to perform the work of digestion for 

 the colony ; while the long thin zooids (dactylozooidsj are 

 specially modified to catch prey, which they convey to the 

 mouth of the gastrozooids. The food digested by the gas- 

 trozooids circulates in canals in the ccenenchyma, and is 

 thus distributed all over the colony and to the dactylo- 

 zooids, just as in other Hydrozoa. 



In the Siphonophora^ which are represented in the col- 

 lection by the glass models of f hysophora^ Apolemia, 

 Agalmopsis, Halistemma, and Physah'a, the entire colony 

 is freely locomotive, usually near the surface of the open 

 sea, and the physiological labours of the colony are allot- 

 ted to separate groups of units or " persons," each of which 

 becomes specially modified for the sole performance of its 

 own function. The exhibited specimen of Physophora 

 hydrostatica may be taken as an illustration : here the 

 labour of the colony is much subdivided, and of the polyps 

 some are exclusively devoted to moving the colony about 

 ("locomotive persons") and have a modified Medusa form, 

 others are exclusively concerned with the digestive labours 

 of the colony ("nutritive persons"), and have become 

 transformed into simple tubes for taking in food, others are 

 entirely occupied with the mechanical protection of their 

 fellow-workers, and have become simple shield-like plates 

 ("protective persons"), others are completely engaged in 

 active defence or in offence, and have become changed into 

 long grappling lines furnished v/ith batteries of stinging- 

 cells, while others are " reproductive persons/' and are prac - 

 lically nothing but bunches of egg-capsules. Ail these 



