DEVELOPMENT OF CUCUMARIA ECHINATA 189 
The following table shows the sizes of eggs observed in the 
family by various writers : 
TABLE I. 
Diameter of egg (mm.). 
Egg newly shed 
Ovarian or found in 
Species. Bq. brood-pouch. Observer. 
Cucumaria parva 0-2 — Ludwig (28, 1898) 
C. echinata = 0-44 Ohshima (40, 1918) 
C. frondosa — 0:46 Des Arts (2, 1910) 
Psolus granulosus — 0:5 Vaney (48, 1906) 
Cucumaria ijimai 0:5-0-55 i Ohshima (38, 1915) 
C. crocea 0-6-0-65 0:7 Ludwig (20, 1887; 
23, 1898) 
C. lamperti 0:8 —- Ohshima (388, 1915) 
C. glacialis — 1-0 Mortensen (32, 1894) 
C. lateralis — 1-0 Vaney (48, 1906) 
Pee Gir a bias — 1-0 Cowles (10, 1907) 
C. laevigata 1-0 — Lampert (18, 1889) 
an — 1-34-15 Ackermann (1, 1901) 
Thyone imbricata 1-2 — Ohshima (88, 1915) 
Among the twelve species in the table, there are only two which 
have no brooding habit and lay eggs freely in water, namely 
C. echinata and C. frondosa;; all the others have the 
brooding habit. 
Maturation — Examination of sections of the egg fixed 
immediately after being shed show that the egg has just extruded 
the first polar body (PI. 8, fig. 4, pb), and that the second 
maturation spindle (ps) can be seen orientated either obliquely 
or vertically with reference to the circumference of the egg, 
while the sperm head (sp) has in most cases just entered. When 
the spindle is perpendicular to the surface a conical cytoplasmic 
process is formed projecting into the canal through the jelly, 
through which the first polar body may have been expelled. 
According to Boveri (4, 1901, p. 147) the canal through the 
jelly of the egg of a sea-urchbin, Strongylocentrotus 
lividus, is widened at the maturation period and serves 
as the way through which the polar bodies are given out. 
Selenka (45, p. 167) noticed for the first time a poler body 
in the egg of C. planci and described it as ‘der Kxoth des 
Hies’. The egg of C. normani when taken from among 
