of Foraminiferal Structure. 173 



is bj no means put forth as perfect in all its parts, but simply 

 as embodying what I conceive to be, for reasons already as- 

 signed, as close an approximation to a natural arrangement of 

 the Rhizopods as the present state of our knowledge allows ; 

 and that, having done my best during the course of the past 

 twelve years to test it whenever opportunities occurred, I have 

 not been able to detect any serious flaw in it. It must never- 

 theless be accepted merely as an attempt to reduce the group 

 of organisms in question to something like natural order. 



SUPPLEMENTAEY NOTES. 



Contractile vesicle. — It has always been urged by me that 

 there is more reason for regarding the contractile vesicle of the 

 Rhizopod as an organ whereby the effete residue of the watery 

 fluid absorbed by the animal is first collected, and then 

 discharged by an orifice in the vesicle, extemporized at the 

 moment of extreme dilatation, than for regarding it as a cir- 

 culatory organ. I may therefore be allowed to point out that 

 although the nature of this organ was discussed by me in 

 detail in the ' Annals ' for December 1863, and it was there 

 shown (both on the independent evidence of my friend Mr. 

 Carter, and as the result of my own observations) that the 

 contractile vesicle in Amoeba, Actinophrys, and certain Infu- 

 soria discharges its contents at the immediate surface of the 

 animal's body (my description of the process being accom- 

 panied by illustrative figures), Dr. Carpenter has not scrupled 

 to say, at p. 472 of his work '■ The Microscope ' (5th Edit. 

 1875), that the nature of the process Avas for the first time 

 " fully established by Dr. Zenker in 1867" — and this in the 

 same page in which he shows that he was acquainted with my 

 series of papers in the ' Annals ' upon the Rhizopods, in which 

 the observations were recorded. 



Noctiluca. — In the Report of the ' Challenger ' Expe- 

 dition, published in the Proceedings of the Royal Society, 

 1876, vol. xxiv. pi. 21, there are three figures which are 

 described as representing " true Diatoms^'' to which the 

 generic name of Pyrocystis has been given by the discoverers. 

 I am, indeed, grievously mistaken if these structures bear the 

 slightest affinity to Diatoms, or are any thing else than true 

 oceanic Noctilucce. It would be just as irrational to separate 

 the testaceous from the naked Rhizopods, because the former 

 have hard coverings and the latter have none, as to regard 

 these new forms as distinct from Noctiluca, because they 

 present a delicate siliceous wall. The figures of the elon- 

 gate form, if accurate representations, as they doubtless are, 



