VERMES, CCELENTERA AND PROTOZOA. 167 



of the world ; but had he had the advantage of working 

 with the help of this new monograph, his lists would have 

 been much more complete and useful than they are. Now 

 that we have so much knowledge of the species of Madre- 

 pora, it is to be hoped that some naturalist will before long 

 undertake the task of giving to us a monograph of the 

 distribution of this important and interesting genus. 



Leaving, for the present, matters connected with the 

 progress of our knowledge of the systematic zoology of 

 these groups, and passing on to recent anatomical and 

 embryological research, we find that among recent papers 

 one of the most important is that of Harmer, on the 

 " Embryonic Fission in the Cyclostomatous Polyzoa". * 



Several examples of a process of fission or gemmation 

 of very young embryoes or embryonic forms have been 

 known to naturalists for some little time. One of the 

 best known of these is the case of the earth-worm Lum- 

 bricus trapezoides, investigated by Kleinenberg, where the 

 embryo, whilst still in the gastrula stage, either divides 

 into two equal halves, each of which produces a complete 

 embryo by simple fission, or produces two or more buds by 

 a process of gemmation. 



The production of lateral buds on the Scyphostoma or 

 larval hydra-tuba stage of certain jelly fish belonging to 

 the order of Scyphomedusae may be regarded as belonging 

 to the cases of embryonic gemmation, but an even earlier 

 form of this occurs in Chrysaora and Aurelia, in which, as 

 Busch and Haeckel have shown, numerous buds may be 

 formed by the larvae whilst still in the gastrula stage. 



These facts then prepare us for an account of embry- 

 onic fission or gemmation in a group of animals, such as 

 the Polyzoa. which multiply during their lifetime very rapidly 

 by the ordinary processes of asexual reproduction. 



The subject of the investigation was Crisia ramosa, a 

 species which is common in the water near Plymouth. 

 On the examination of the growing point of a branch of 



1 Harmer, S. F., Embryonic Fission in Cyclostomatous Polyzoa, 

 Quart. Jour. Micr. Set., xxxiv. 



