AGASSIZ AND WOODWORTH: VARIATIONS IN RUCO E. 129 
The youngest specimens of Eucope observed (eleven in number) had 
twelve tentacles in all, one at the base of each of the four radial canals 
and two in each quadrant with a seuse organ, and without any tentacles 
intermediate between the radial and the sense organ tentacle. t is 
possible that these specimens may belong to a different species, as the 
youngest specimens of Eucope diaphana I have raised from the hydroid 
already had 24 tentacles." But of course it is possible that the above 
stage may have dropped from the reproduetive calycle at an earlier stage 
of development. 
Were the marginal tentacles to develop regularly we should have as 
the third stage a Eucope with 48 tentacles, a fourth stage with 96, 
and a fifth stage with 192. 
But as far as our experience shows, we find normal Eucope only in the 
first and second stages, and even then there are numerous variations. 
The formule for the normal stages are, calling T any marginal 
tentacle, 
Te, the primary tentacle at tho base of the radial canals ; 
To, the primary tentacle with a sense organ at its base; 
U, the first set of marginal tentacles appearing between T, and 79 
the stage with 24 marginal tentacles ; 
tə, the second set of marginal tentacles on each side of t, in the stage 
with 48 marginal tentacles ; 
ts, the third set of marginal tentacles on each side of £j, in the stage 
with 96 marginal tentacles ; 
t4, the fourth set of marginal tentacles on each side of £4, in the stage 
with 192 marginal tentacles ; 
ts, the fifth set of marginal tentacles on each side of „ in the next 
stage with as many (theoretical number 31 tentacles) as 1645, 84% 4ts, 
2t,, 14, tentacles between the (T, and T,) radial canal and sense organ 
tentacle, or 95 tentacles in each quadrant between the radial canals, or a 
total theoretical number of 384 marginal tentacles. l 
The formula of the youngest stage, or first stage, would be 
X (4) T, + (4) 2 Ty = 12 T, 
or two tentacles with a sense organ in each quadrant. 
That of the second stage, 
X (4) T, + (4) 2 To + (4) 36 = 24 T, 
or two tentacles with a sense organ in each quadrant with a tentacle of 
the ei order between each and the radial canal and sense organ. 
1 Proc. Boston Soc. Nat. Hist., June 4, 1862, p. 92. 
