14 BRITISH HYDKOTD ZOOPHYTES. 



power of reproduction by means of ova.* 

 This order of reproduction is usually described 

 as "Alternation of generation," and this is the 

 earliest instance of its occurrence in the animal 

 kingdom. It is very important to realize these 

 steps, more especially as they are to a great 

 extent obscured in many instances. We will 

 therefore enumerate them thus : 



The *' Alimentary" polypite. 1. — Ali- 

 mentary Polypite. The ordinary colonial 

 polypite, whose only duty is to obtain and 

 assimilate food for itself and the colony, but 

 which takes no part in the work of propaga- 

 tion. 



The "Select" polypite. U.f— "Select" 

 Polypite. Certain of the above, which, 

 for reasons stated in the foot-note, we 



•It is extremely interesting to note the parallelism with 

 this order in the plant world. For exanaple: Amongst the 

 Ferns (Cryptogams), if one of the spores fonnd on the back of a 

 frond be sown, the result will not be a fern, but a very small 

 and simple plant — a leafy expansion, r. lied a prothalium. It is 

 the function of this little plant to produce the male and female 

 elements ; and so soon as fertilization has taken place it dies 

 leaving the embryos (" oo-spheres '') to develop into proper 

 ferns . 



tThe "Gonoblast" idea of Huxley and the "fertile 

 pol3rpite" of Hincks. Some apology seems necessary for 

 presuming to suggest a more suitable term for these Buds, in 



