20 SALENIA VARISPINA. 
These delicate processes appear, however, to be soon either worn oflF or 
broken, as in specimens measuring from 2 to 3 mm. in diameter we generally 
find only an occasional primary spine still retaining the filiform processes, or 
a trace of them. As the spines become older, these processes are little by 
little changed to the sharp spiny processes figured as characteristic of S. 
varis/nnu. The primary spines of these young stages are also marked for the 
single prominent verticillation formed near the base of the shaft by the some- 
what stouter filaments of that portion of the radiole. 
The young spines found on the small primary tubercles near the abacti- 
nal system on the ambulacral and interambulacral areas have a striking 
appearance. They recall somewhat the fan-shaped, short spiny radioles 
found on the test of very young specimens of Strongylocentrotus ; they also 
recall the peciiliar umbrella-shaped spines of Aceste, and of some deep-sea 
Ophiuran.s. The jjrimary spines, when the shaft has as yet but a single pair 
of filaments, could readily pass for modified pedicellaria) ; they also resemble 
the hook-like appendages of the Ophiurans. In the next stage the radioles 
carry from four to five processes, when the central part of the shaft begins 
to increase in length ; with this increase commences also the formation of 
the filaments, so characteristic of the large primary interambulacral spines 
of the young stages. The primary interambulacral spines are usually simi- 
lar, but .shorter, slender-pointed radioles, with from six to eight processes and 
a ring of filaments near the base of the shaft. In the ^'oungest stages there 
are as yet no papillae ; these appear only later, in larger specimens, and at 
first show no trace, in the interambulacral areas, of their regular Cidaris- 
like arrangement round the base of the primaries, as in the older stages. 
The papilla3 when they first appear are short slender-pointed spines, with 
short, sharp processes, covered by lines of pigment-spots of dark violet. 
With the growtli of the test these papillas become club-shaped, curved, 
and finally flattened and fan-shaped, as they appear in the older Saleni». 
The papilh^ of the anal plates are articulated in tlie older specimens; at 
first they are sessile, like the embryonic spines (club-shaped sessile papillte) 
covering the plates of the genital ring ; with the increasing size of the 
young Salenia they resemble more the coronal papillae. These abactinal 
sessile papilte are interesting, as they develop exactly as do the embryonic 
spines in young Echini, from the general granulation of the plates; but 
they remain, as in the Arbaciadae, always sessile. 
As I have stated, the genital openings are not yet formed in young speci- 
