204 CAPTAIN OWEN ON THE SUBrACE-EAUNA OF MID-OCEAN. 



water, to enable them to rise again to the surface. "Whether the 

 living Polycystina are to be found at the bottom of the ocean can 

 only be determined by deep-sea dredgings. 



It will naturally be asked if I can throw any light on the pro- 

 pagation of the race. It is a subject I touch upon witb some 

 diffidence; but I must not pass by this very interesting topic 

 without giving what little information I have been able to gather 

 by a long and diligent search. Eare have been my opportunities 

 of witnessing anything that seemed to elucidate this matter ; but 

 still sufficient has presented itself to enable me to offer or rather 

 perhaps to hazard an opinion ; but my facts and specimens may, at 

 all events, be of some value. 



I would refer to the mode in which two Diatoms or two 

 Desmidiacese will unite, and how the contents of one will pass 

 into the cell of the other. With Diatoms, &c., this process has 

 been easily watched ; with the rarer Polycystina such opportunities 

 have been more difficult to obtain. I have seen the conjunction 

 of two individuals, the yellow sarcode appearing as two separate 

 yelks, one in each shell. One of my specimens shows the line of 

 junction very distinctly, and, I think, proves that such specimens 

 must not be taken as single individuals of another species. An- 

 other represents a similar case, in Avhich only one shell is filled 

 with the sarcode, the other being quite empty. A drawing was 

 taken by me while at sea from a specimen in the live-box : this 

 proved to me that the sarcode had not contracted in drying and 

 thus filled only a portion of its original space. In a dead and 

 dried specimen this might have been contended for. As I have said 

 before, the thing is rare to witness ; and it wiU require the evidence 

 of other careful observers to clear up this point entirely to ou j 

 satisfaction, for I hold it to be a matter of great interest. 



In the cases I have observed, the siliceous shells appear to 

 closely unite ; they might be easily mistaken for one individual, 

 if seen only in the fossil state, or after having been subjected to 

 the action of nitric acid. It was the fact of the sarcode being 

 found in only one portion that first gave me a clue to its real 

 nature. I say real, provided always I am right in my conjecture. 



The shells of some of the globular forms of the Polycystina, 

 whose conjugation I believe that I have witnessed, are composed 

 of a fine fretwork with one or more larger circular holes ; and I 

 suspect the junction to take place by the union of two such 

 apertures. That the figures of these shells become somewhat 

 distorted or elongated, and the passage of communication en- 



