654 MR. J. LEWIS HOXIIOTIC OX TIIK [^^l"'- I-*? 



criticised my paper and comes to tlu; conclusif/n that my ('(fort 

 has not cleared up tlie coufiisioii and tliat all these rats belong to 

 one and the same species-^- J/«6' rattas. 



Dr. Hossack's remarks, fair and just .is they ajjjjear to be, f:ul 

 from the fact that we were, vvoi-king at the sid)ject from entirely 

 diflerent points of view — he as a meilical man, anxious to know 

 tlie number of species by whicli the plague might be conveyed — 

 1, as a zoologist, .seeking for a. law and order in the apparently 

 innumerable varieties found among these rats. For ])r, H^s- 

 sack's purpose it is sufficient to know tliat there ai'e but two 

 species of true rats, usually found in houses — the short-tailed, 

 heavy-built and practically invariable Mus norveyicus, and the 

 long, slender, and exti-emely variable Mtts raittis, which includes 

 aJl the varieties beai-ing the mass of names that so confused my 

 Clitic. Had he written to me in the first place, I could have told 

 him at once that all these long-tailed rats belonged to one vei y 

 variable species, and that in the large towns, where ail his 

 material was procui'ed, no order or classification was possible as 

 the varieties had become hopelessly mixed and crossed, but that 

 in the country places the varieties were much better defined, 

 and apparently bi'e<l true. The question of the classification and 

 study of these varieties is a specialised study for zoologists, and it 

 is not to be expected that a medical man, studying the plague, 

 should be able to devote the time necessaiy for the thrashing out 

 of such matters. 



It would therefore have been better had he applied to recog- 

 nised authorities for his information, rather than attempt a task 

 in a specialised subject oiitside the scope of his investigations. 



I am glad to have had this o])portunity of replying to 

 Dr. Hossack, for many people do not yet realize that the study of 

 geographical forms and minute vai-iations has a very great bear- 

 ing on many large and important zoological problems, but need 

 not concern the man engaged on other cognate investigaticms, and 

 in the present instance it is sufficient for him to know that all 

 these vai'ieties of the long-tailed rat lielong to one si)ecies, J/ its 

 rattas. 



Mus rattus /;/ lujiipt. 



In Egypt we find two distinct forms of M^is ratttis — the one 

 with pvn-e white underparts and white feet, which was named 

 Mitji tactorKni.'^' by Savi ; and the otlier with slate-gre}'' underparts 

 and dark feet, which may be known as Mas (dcraudriinisf. 

 Between these two forms many intermediates occni', the actual 

 typical forms being comparatively rare J. 



* 3fvs tectorum Savi, Nuovo Giorn. Pisn, 1825. 



t Mus nlexandrhnis Gcott". Descr. dc I'Egypto, llist. Nat. ii. p. 733 ; Atlns, pi. v. 

 %. 1 (1812). 



X 'riii'^ stiiti'mciit ai)pnvciitly contradicts tiio ivinaiks on p. 053, but it must ho 

 borne in mind tbiit tliosc reniavks \vcn> bused on Maliiy niatcrial, obtained in centres 

 removed fnnn tbe intluenco tif foreiifn sliipi>in;r, whereas in tbi> i)resent case tl;p 

 s|)ecimens came from ' itojinlous centres, conti;;nous to .-i biriri' waterway- (tlie Nile 

 and its brancb''s). 



