26 



T. C. WHITE ON THE AQUARIUM 



But the third and rarest form of multiplication consists in the 

 ejection of ova, and this I was fortunate enough to witness in my 

 Aquarium. It occurred in a specimen of Bunodes gemmacea, which 

 had taken up a favourable position close to the glass. I was attracted 

 to it by noticing a drab-coloured stream of ova pouring from its 

 mouth and falling in a heap at its feet ; upon more closely examin- 

 ing the creature with a pocket lens I found it distended with water, 

 and the tentacles especially so, while globular bodies were circu- 

 lating up and down the interior of them, but did not pass out at 

 their extremities. I examined some of these bodies under the 

 microscope, and found them opaque, and non-ciliated spheres filled 

 with granular contents. I had hoped to have seen the develop- 

 ment of these ova into the adult form, but, as in Mr. Gosse's ex- 

 perience of similar ova, decomposition speedily set in. Dr. Spencer 

 Cobbold was more fortunate, and in the annals of " Natural 

 History" for February, 1853, he describes the various changes 

 through which these ova at last arrive at their final shape. A de- 

 pression takes place in the surface of the globose embryo, which 

 becomes the general cavity, the edges become incurved, and descend 

 into the cavity, forming the stomach ; septa spring from the inner 

 wall beginning from the summit and extending downwards, and ten- 

 tacles bud from around the mouth. He made these observations at 

 a continuous sitting occupying the whole of one night before decom- 

 position had commenced its attack upon them. I once saw the ejec- 

 tion of ova in a Serpula ; noticing occasional bursts of cloudy matter 

 from the centre of its plumose branchia?, I collected some of it by 

 the dipping tube, and found it consisted of an immense number of 

 minute orange-coloured globules, each enveloped in a clear sac of a 

 probably albuminous nature. I was not fortunate enough to trace 

 out the development of these ova, but I shall hope to do so at 

 some future time by means of a method I have the last few months 

 adopted. I place ordinary microscopical slips of glass in various 

 parts of my Aquarium, and especially near such objects as are 

 likely to eject ova or to develope a stem like the Polyzoa, and 

 then they can be taken out and examined under the microscope, a 

 drawing made of any developing form, and replaced to undergo 

 further examination as changes advance. In this manner I 

 have been much interested in watching the growth of Foranii- 

 nifera, which have attached themselves to these slips, and which, 

 apparently, have not suffered from the trip they took out of the 



