MEMOIUS OF THE NATIONAL ACADEMY OF SCIENCES. 



387 



Table ii — Continued. 



(Locality : Naasaa, N. P., Bahama Islands. ] 



Habitat 



Green Oreen 



spttDge. spou<j:e 



Sex. 



Number in Table 1 



Length of |iropodiiH of large chela 



Leiifjth ofHaiiio to s|«iuo at base of dactylo 



Grealest width of saiiio 



Grivite.st dejilh of s.'iiiip 



Width of sarr.o at spiiio, at base of dactjio 



Length of " llmrnl. " of propodus 



Length of dactylo 



Width of same, over tooth 



Length of carpus of largo cheliped, ou upper me- 

 dian line 



Length of nieros of same 



Greatest width of nieros of same 



Length of propodiis of small cheliped 



Length of same to articulation of dactyle 



Greatest width of same 



Greatest dejith of same 



Length of dactyle of same 



Width of dactyle of same 



Length of carpus of same 



Length of meros of same 



Greatest width of meros of same 



Length of carpns of second jioreiopod 



Length of tirst segment of carpus of same 



Length of tifth segment of carpus of same 



Length of second, third, and fourth segments of 

 carpus of same 



Length of propodus of same 



Length of meros of same 



Length of propodus of third pereiopod 



Length of carpus of same 



Length of meros of same 



Length of i rotopodite of third pleopod 



Width of same 



Length of endopodite of same 



(Jreatest breadth of eudopodite of same 



Length of exoi)odito of uropod 



Breadth of same 



Length of eudopodite of uropod 



Breadth of same 



15 

 II 



4 



4.f> 

 5.'* 

 4 

 3 



2.8 

 5.5 

 :i 



().7 



4 



2.4 



l.H 



H 



1 



2.3 



G 



2.7 



7 



4 



1 



2 



2.2 



5.1 



5 



2.8 



6.2 



6 



1.2 



8 



2 



.5.8 



4.2 



5 



3.5 



16 



11 

 6.1 

 4.6 



6. 5 



6 



3 



2.4 



5.3 



2.6 



6 



3.1 



2 



3 



n.i) 



4.6 



2.7 



5.8 



1.9 



1.5 



3.5 



1.6 



4 



3.7 



3.7 



9.9 



Rorkn: 



Dis I't. 



Ri-if. 



Rockfl : I Rocks 



Grnen K<'V Oreen Key 



Reef. " Reef. 



:>. I 



1 



3 



1.7 



2.2 



1.8 

 0. 9 



1 



1.9 



3 



0.8 



•I. 7 

 4.4 

 2.5 



2 

 1 



0.8 

 '2 r. 



2 



l.H 

 0.8 



1.8 

 0.8 

 0.6 



n_„_„ I Rocks : 

 "P""""- Keef. 



4.5 

 3.4 

 2 

 1.4 



0.6 

 2.0 



4.5 



3.4 



2 



1.4 



1 



0.6 

 2 



1.7 



6 



4.4 



2.4 



2.0 

 1.5 



1.3 

 1 



1.7 



7.7 



VII. — THE CAUSES AND SIGNIFICANCE OF VARIATION IN ALPHEUS SAULCYI. 



If we consider Nos. 1 or 2 of Table 1 as representinjr tbe nearovSt api»roacli to the mean of tbe 

 species, Nos. 5 to 15 must stand for individuals which have iluctuated farthest from the mean. 



The individuals given in the table were chosen without reference to sex, yet it appears that 

 nearly two-thirds of the number are males. In examining a larger collection of these aberrant 

 forms 1 find a still greater percentage of males. There can bo little doubt that in tho.se cases the 

 males are in the excess, although I have not tested this point carefully. It is also evident from 

 observation and detailed measurements that the average size of these abnormal individuals is less 

 tliaii one-half that of the brevicarpus type. The brown sjjonges teem with a po[)ulation of uiider- 

 sizA'd forms, nearly all of which are aberrant, and none of those which were examined exceeded 

 tlie length of 17.5""", which is considerably less than the average for the type. 



Dow far are these variations individualistic and how far are they confined to the race or 

 species as a whole! In other words, is the individual plastic, dei)artiiig from the standard of tlie 

 species and becoming ditterent at different i)eriods of its life, or do individuals tleviate from the 

 pieau of the species, each along its own line ? Further, are the variations cougenital 1 While we 



