290 
W. M. Wheeler 
and sequence in the ripening of the sexual products has long been 
known to occur in many other hermaphrodite Metazoa^. 
How is this asynchronism in the maturation of the sexual products 
to be explained? Some authors, approaching the phenomenon from 
the physiological side, would regard it as due to an unequal dis- 
tribution of nutriment to the reproductive organs: during one period 
1 Omitting all reference to the general Statements concerning dichogamy 
to be found in our standard text-books of Zoology, I give here a list — prob- 
ably very incomplete — of the cases which I have been able to gather from 
special papers, for the purpose of showing the wide distribution and frequency 
of the phenomenon. Several of the references have been drawn from recent 
papers by Pelseneer ('94) and Montgomery ('95): 
Porifera: Spongilla (C.Keller '78); Aplysilla (v. Lendenfeld '83, pag. 261 . 
Cnidaria : Hydra (Ecker '53 ; Marshall '82, pag. 669). 
Platyhelminthes. Acoela: Convoluta (Claparède '61, pag. 128) ; Bhabdocoela: 
Gr affilia (Böhmig '86, pag. 315; v. Ihering '80, pag. 147); Fromesostoma 
and Macrostoma (v. Graff '82, pag. 127); Stenostoma (J.Keller '94, 
pag. 377 and 398) ; Tricladidea (Hallez '79, pag. 43); Bipalium Loman 
'88); Polycladidea (Lang '94, pag. 1091); Trematoda (Ercolani '82, 
pag. 43); Cestoda: Solenophorus (Roboz '82, pag. 263) ; Nemertini: Fra- 
rhynclms (v. Kennel '83; MoORE '95j; Tetrastemma (Marion '74); Sti- 
chostemma (Montgomery '94 and '95). 
Nematoda: ^Z/«>?^o?2ema (Leuckart '87); Filaria (ZUR Strassen '91, pag. 439). 
Annelida. Polychaeta: OpÄri/o^rocÄa(KoRSCHELT'93); Myzostomidae: Myzostoma 
(Prouho '92; Wheeler '94). 
Mollusca: Limnaeus (ElSiG '69) ; Agriolimax agrestis and melanocephalus (BaboR 
'94); Cymhulia (Leuckart '54); Cymhuliopsis (Peck '90); Desmopterus 
papilio (Chun '89) ; Clione limaciim, Clio striata^ Fjobiger, Folis, Elysia 
(Pelseneer '94) ; Entoconcha (J.Müller '52); Neomenia (Wirén '92); 
Solenopus (KoREN & Danielssen '77); Ostrea edulis (Davaine '53; 
P. J. VAN Beneden '55). 
EcMnoderma : Asterina gibbosa (CuÉNOT '88; Lang '94, pag. 1091); Synapta, 
Anapta, Chirodota (LANG '94, pag. 1091); Amphiura squamata (LANG 
'94, pag. 1091). 
Crustacea. Cymothoidae: Nerocila, Cymothoa, Anilocra (Bullar '76 and '77; 
Paul Mayer '79); Cryptoniscidae (Kossmann '84).' 
Chordata: Myxine glutinosa (CuNNiNGHAM '87 and Nansen '88); Chrysophrys 
(Brock '78). 
Protogyny, or the opposite sequence in the maturation of the sexual pro- 
ducts, i. e. the earlier maturation of the female and later maturation of the 
male cells, is very rare in the animai kingdom. The only cases which I have 
met with are those cited by Pelseneer ('94) and Montgomery ('95), viz. the 
Turbellarian Microstoma lineare (Rywosch '87 and '89), the Pulmonates Limax 
maximus, Malacolimax tenellus (Babor '94) and Agriolimax laevis (Babor '94 
and Brock '86) and the Tunicate Salpa (Krohn '46). A similar preponderance 
of the protandrous over the protogynous sequence has been observed in flower- 
ing plants. 
