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PACIFIC SCIENCE, Vol. XXII, October 1968 
Fig. 1. Eukrohnia bathyantarctica. A, Dorsal view 
of a full mature specimen; the ova arranged in two 
dorso-ventral rows; brood sac incipient. B, Posterior 
part, dorsal view; marsupial sacs (brood sacs) filled 
with eggs containing embryos in a single coil (Stage 
III). C, Posterior part, dorsal view; brood sac broken. 
Conant (1896) witnessed the egg laying of S. 
his pi da Conant at Beaufort, North Carolina. The 
eggs remained 20 to 30 minutes in each oviduct 
while a jelly coat thickened around each of 
them. They were pushed out by ovarian contrac- 
tion and issued in two linear rows (one for each 
oviduct), totalling from 60 to 70 eggs. 
Stevens (1910) observed the free discharging 
eggs in S. elegans Verrill. Huntsman and Reid 
(1921) found eggs of S. elegans , in various 
stages of development, free in the plankton of 
the Bay of Fundy and the Gulf of St. Lawrence. 
Ghirardelli (1954) stated, "Anche le Sagitte 
depongono uova pelagiche spesso riunite in 
piccoli ammassi gelatinosi, talvolta pero anche 
isolate.” 
Murakami (1959) observed in the laboratory 
specimens of S. crass a Tokioka in the process of 
free spawning of eggs. Elian (I960) observed 
eggs of S. setosa J. Muller and S. euxina Molt- 
chanoff free in the plankton from the Black Sea. 
Thorson (1936), Werenberg-Lund (1947), 
and MacGinitie (1955) suggested that the arc- 
tic animals show a tendency to brood their eggs 
or to provide some other method of protecting 
them until the embryos, the young larvae, or 
young animals develop. Ghirardelli (1959 h') 
made similar observations for both the arctic 
and antarctic Chaetognatha. However, the spe- 
cies of Eukrohnia possess the brood pouch, and 
have world wide distribution (except E. bathy- 
antarctica which is mainly restricted to the an- 
tarctic-subantarctic regions), inhabiting different 
depths. The temperatures in the regions in- 
habited by the species are in many cases similar 
to those encountered in the Bay of Fundy or the !| 
Gulf of St. Lawrence, where free eggs of S. 
elegans at various stages of development were 
observed (Huntsman and Reid, 1921). 
Thus it appears that the eggs of the species 
of chaetognaths belonging to the genus of high- 
est evolutionary rank are probably better 
equipped for survival, either by means of the 
chemical composition of the vitellus or by the 
nature of the involucrum of the egg. 
Table 1 is a summary of the breeding char- 
acteristics of the Chaetognatha which may have 
some evolutionary significance. 
I wish to express my appreciation to Professor 
