9f> M I'll I -11 < \ Al:l \TlM\. [I'AKT I. 



4. Branchipua and Artemia. A- it has been alleged that variation may be pro- 



due. d HI tl. tatiMn i.f the abdomen of these animals by changes in the 



a whi.-h th.-y live, it * -ary here to give the facts on which thi- state- 



iij. : ith.T i|iu -tion of the relation of Arti-min .-<////(" to A. util- 



itli this subject, that though not strictly cognate, 

 unit f tin- r\i.l.-nrr on this point also must be given. 



,.i A n -ni 1 published certain papers on variations of 



.1,7. H.I in. In- es in the Mliiuty of the water in which the animals 



h\,,|. i la great deal of interest and have often 



.ml ]p.i|nilar writers. The facts have thus .-it tiim-s 



i.l so much exaggeration has en pt in, that l.eioie 



it will IH- well to five Schmankewitsch'a own account. 



ted that Schniaiik. v. it-.-h observed the conversion of Hnuii-hijnix 



int., I ,.f Artemia ...;//;ci into A. milhauxenii following upon the pro- 



i ..f tin- waters of a salt lake. Strictly speaking howeve* this is 



Srhmaiik. witsch. His story is briefly this: That tli.- salt 



Kiiyalm. 1 liy a diim into an upper and a lower part : the waters 



in th. latter In in/ satmated with .-alt, while the waters of the upper pan were less 



-alt. I'.y a -piin/ tl.....l in tin- y. ar 1*71 the waters of the upper part of the lake 



the 'lam ai i .1 the density of the lower waters to 8 Beuum. 



(=.i: ; u.'.li, au.l iii tin- water great numbers of A. xnUiin then appeared, 



numbly hi\,!i i...ii wa-h.-.l in from the upper part of tin- lake, or from the 



hi. mil in After tin- th.- .lain was made good, and the wat. is of the 



r laki- by evaporation became more and more concentrated, bring in the summer 



..f 1*7-' i i i; .about .-p. g. l-lti:{. ; iii 1-7:5, 1HB (about sp.g. l-l:;.">i: in August 1-71, 



1 , , ind lati i in that year tin- salt bewail to crystalli/.r out. 



In 1*71 tin- Art, -mi:, hud caudal tin- of _-."" 1 size, h. arin^' s to TJ, iar.lv 1.",, bristles, 

 but with th- i-oiirriitiation ..I' tin- watrr tin- gi-m-i ation- uf Arlt iniii 



i, until at tin- end of the summer of 1*71 a large part of 

 i had no caudal I'm-, thu> pir-i iitiii^.' tin- charai ' > ot A. milhausenii Fischer 

 and Milin- Kdw. Tlir -iii-ci --ivr >ta!_'.-> of tin- diniiimtion of the tail-tins and of the 

 numhiTs of tin- bristli - an- -hrwn in thr ligurr-i, with which all are now familiar. 



, i."lur. .1 rx|.i-iiiin ntally by gradual concentration of water, 



inmr foi in i.-.-mbling .1. inilltiiiiai-nii. It was found also that if 



tin- animals without caudal tin- wnr krpt in watrr which was gradually diluted, 



after M.iiie w..k- ;L j.air ..f conical ].romiiu-ncos, each bearing a single bri-tle, ap- 



I'. .-.r- .1 at the end of thr abdomen. 



It is fuitlier Mated that tin- branchial plates- of the animals living in the more 

 highly con.-, ntiat. d wat. r wen- materially larger than those of animals living in 



r of :i lc-s conceiitra: 



Schmaiil.i wit-ch K - on t.. -;iv that by artilicially brrrding Art, 'mid xnlinn 



in more and more dilut. d salt water he obtain..! a form having the characters of 



> IIVMI me Input, and that li. i- this form as a new species of 



Ili-inii-lufiii*. lie ex].lain- tin- -lad ment thu-: In the normal Artrinin, the last 



..-nt uf tin- p..-t abd ....... n i> about twice a> loim- as . ,-ich of the other M-L'iiiriits. 



\vhilr tb- iingjiait in Hriini-lii fnm isdividid int. . two segnif-nts. He states 



that in his i. [union the condition of the la-t .-egmnit of the po-t-abdomen consti- 



ial dilTt-reiic.- betwe.-n Arti-mni and I'-rinichijnut, and that such 



diM irred in the third generation of the fonn jiroduced 



by him from Art,-niin b;. i\r .lilution ,,f the watrr. A s.-cond distinction 



betw.-.-ii tin i in iii. \rt,miii is reproduced partheno- 



ily, while Itr.nii-liijiii* is not known to be so reproduced. As to the 



i .-litmn of hi- new loim in tin- i. ~\- ot, S.-hinankewitscli had no evidence. 



'i. nt piper. /.. f. . '/... 1*77. further paiticulars are given, re- 



> tin- natural \ ai i- ; i. - of .1 . ,-,///,, . ( )f t hr-e lie distinguishes two, 



\ar. '/ an-i vai /-. The iir-t of t In -e i- distin-.-ui-lied by its greater size (8 lines 



iii-t. in.-, tb. for tin- type) and bv tin- greater lei. the post- 



-ui. n. In the type the bi;-tles on each caudal lin air :'. m-rallv S 12, and in 



. /. . /.. \x\., 1>7."., L'. p. inn and xxix., 1-77. p. l'_".i ; also in several 

 :;in publications, to winch n t. Brill be l.nind I.e. 



1 i ' thl point a ; ...... 1 deal of intrr. Ming evidence i- given iii Schmanke- 



ut as it does nut hear immediately on the ijiu-Mioii of the specific 

 dii' : b. . n introduced h< i. . 



