SPONGES, ZOOPHYTES, AND SEA-FIRS. 



49 



on all sides like little bunches of grapes. The colony is 

 invested with a straw-coloured skeleton, and as the stems 

 are unbranched, each resembles an "oaten pipe." The stems 

 are not ringed, and 

 narrow towards the 

 base, where they are 

 twisted and inter- 

 laced. The zooids are 

 bright pink, and pro- 

 ject like beautiful 

 flowers from their 

 straw-like tubes. 

 Besides T. indivisa 

 with its unbranched 

 tubes there are 

 several other species 

 of Tubularia, but 

 these come from 

 deeper water or are 

 less common. The 

 large size of the 

 zoophytes and the 

 beauty of their 

 colouring make T. 

 indivisa one of the 

 most beautiful of our 

 Hydrozoa. Each 

 sporosac contains 

 only a single egg, 

 which undergoes the 

 early stages of its de- 

 velopment within the 

 sac. The embryo, 

 when set free, has 

 some slight power of FlG 

 independent loco- 

 motion, and must also be readily carried about by currents. 

 We come next to the true sea-firs (Calyptoblastea), in 

 which the skeleton reaches a much higher degree of de- 

 velopment, and which are, above all, remarkable for their 

 delicate tracery. Many of them, as they spread out in the 



W. Colony of Tubularia inoivisa, showing 

 the zooids in their tubes. After Allman. 



