GERM CELLS OF HERMAPHRODITES 193 
Proterogyny has been described in certain ascidians 
(Salpa), pulmonate gasteropods, and corals. That 
hermaphrodites are not sexless but really animals 
with double sex is well shown by the life history of 
a worm, Myzostoma pulminar, which passes through 
a short male stage during which spermatozoa are 
produced, then a stage when no functional germ cells 
are formed, and finally a female stage, characterized 
by the development of eggs (Wheeler, 1896). Thus, 
in this species, although hermaphroditic, there is no 
functional hermaphroditic stage. All variations be- 
tween this entire separation of the periods of germ- 
cell development and the simultaneous production 
of male and female germ cells have been recorded. 
Some degree of protandry has been observed among 
the sponges, ccelenterates, flatworms, segmented 
round-worms, mollusks, echinoderms, crustacea, and 
chordates. 
Hermaphroditism may occur in only a few families, 
genera, or species inaclass. This is true, for example, 
among the anthropods and vertebrates. Normally 
the insects are called dicecious, but among bees, ants, 
and butterflies, and more rarely other groups, individ- 
uals appear which exhibit male characters on one side 
of the body and female characters on the other, or the 
anterior part may be male, the posterior female, etc. 
(von Siebolt, 1864; Schultze, 1903; Morgan, 1907, 
1913). Such a phenomenon is known as gynan- 
dromorphism. Several hypotheses have been pro- 
posed to account for this condition. Boveri has 
suggested that if the egg nucleus should chance to 
ce) 
