357 



CORRESPONDENCE. 



Time and Change in Foraminifera. 



1 cannot permit the observations made in the March number of Natural 

 Science (p. 153 ante) respecting some criticisms I made in the Revue critique de 

 Palcontologie on the recent work of Messrs. Rupert Jones, Burrows, Chapman and 

 others on the Foraminifera of the Crag, to pass without making some reply 

 thereto. 



I am sorry not to have expressed myself " with the lucidity of my nation" ; 

 what I meant to say was that descriptions of fossils to a large extent fail when they 

 do not recognise separate species as such. The palaeontologist should seize upon 

 every convenient opportunity to distinguish species where they characterise 

 horizons or geographical provinces. In the present instance I may remark that 

 when such a careful observer as Mr. Schlumberger definitely states that he can 

 separate Eocene Foraminifera from those now living, and describes and figures the 

 differentiating characters, palaeontologists surely must accept his work or say in 

 what way it is at fault. Mr. Schlumberger shows us that under the name of 

 Bilocidina ringens, which Lamarck proposed for an Eocene species from the Paris 

 Basin, two living species have been confounded, to which he gives the names 

 Biloculina sarsii and B. bradyi. In like manner the living Bilocidina hulloides, 

 d'Orbigny, must be distinguished from the fossil species and becomes B. anomala, 

 Schl. and B. lucernula, Schl. ; and many other examples could be quoted. Palaeon- 

 tology teaches us that throughout long periods of time animals usually undergo 

 some change, so that before assigning a species to one belonging to a different 

 stratigraphical horizon, or to another geographical province, it is necessary to study 

 that species very carefully and to give it the benefit of any differentiating characters 

 that may be found to exist. It is better to err in recognising these differences as of 

 value in separating species, than to submerge them and thus invite worse confusion 

 in the distinction of species. I am a little doubtful whether the learned authors of 

 the " Crag Foraminifera " have not contributed to our difficulties in the manner last 

 mentioned. 



Gustave F. Dollfus, 

 Paris, March 18, 1897. P°^- Corr. Geol. Soc. 



[We are in full accord with the position assumed by Mr. Dollfus in this 

 interesting letter. It must of course be left to the specialists engaged in the 

 discussion to decide as to the specific independence of each form studied. All that 

 we maintained was that difference of locality or horizon was not in itself sufficient 

 ground for separating species. Some palaeontologists do not seem to have very clear 

 ideas on this matter. — Ed. Nat. Sci.] 



POLYCH.^TA in THE CAMBRIDGE NATURAL HiSTORY. 



May I point out some mistakes on the part of the writer of the Review, in the 

 March number of Natural Science, of the section on Polychasta contributed by 

 Dr. W. B. Benham to the second volume of the Cambridge Natural History. 



The Reviewer draws up a somewhat alarming list of "Certain errors (inter alia) 

 in general anatomy." The inclusion of Haplobranchus amongst the hermaphrodite 

 Amphicorinidae is certainly erroneous, as pointed out ; but let us examine the other 

 alleged "errors " seriatim. " The septa of the body are not so complete as to isolate 

 the compartments . . the parapodia are essentially hollow organs, facts not 

 explicitly stated " — if Dr. Benham's statements are not sufficiently clear on these 

 points, they are not erroneous, but incomplete. " Prostomial tentacles are probably 

 not restricted to the sub-order Nereidiformia " — a fact the reviewer might have 



