242
J O H N R U N N S T R Ö M
FIG. 14. Cortical particles of Strongylocentrotus
purpuratus. Lowest arrow, extralamellar body; middle arrow, basal region of lamella; uppermost arrow, lamellar
filaments. X 50,000. (Harris.)
the extralamellar bodies. The filaments within the lamella have a helical
configuration (Motomura, 1960, Figs. 1 and 2 ) , but a concentric structure is also found which comes closer to the pattern in S.
droebachiensis
Hoc. cit., Fig. 3 ) . I t is probable t h a t two different pathways are open
in the morphogenesis of the lamella in H. pulcherrimus.
I t would be of
great interest to know the relative frequencies of the two morphogenetic
pathways. A similar bifurcation was found in Paracentrotus.
Figure 11
represents, as described above, a case where the concentric arrangement
of the lamellar branches predominated. The probability of this type is,
however, not as great as t h a t of the type with coiled filaments. Afzelius
(1956, Fig. 4) found in an egg of Spatangus purpureus a case of a some-
J O H N R U N N S T R Ö M
FIG. 14. Cortical particles of Strongylocentrotus
purpuratus. Lowest arrow, extralamellar body; middle arrow, basal region of lamella; uppermost arrow, lamellar
filaments. X 50,000. (Harris.)
the extralamellar bodies. The filaments within the lamella have a helical
configuration (Motomura, 1960, Figs. 1 and 2 ) , but a concentric structure is also found which comes closer to the pattern in S.
droebachiensis
Hoc. cit., Fig. 3 ) . I t is probable t h a t two different pathways are open
in the morphogenesis of the lamella in H. pulcherrimus.
I t would be of
great interest to know the relative frequencies of the two morphogenetic
pathways. A similar bifurcation was found in Paracentrotus.
Figure 11
represents, as described above, a case where the concentric arrangement
of the lamellar branches predominated. The probability of this type is,
however, not as great as t h a t of the type with coiled filaments. Afzelius
(1956, Fig. 4) found in an egg of Spatangus purpureus a case of a some-