572 



John Beard 



and stomaci! , inhabitiüg two pouclies formed on the under side of ber 

 valves; 3) hermaphrodites with occasionally one, two or three males. 

 capable of seizing and devoiiring tbeir prey : 4) and an hermapbrodite 

 Scalp. vtdgare with »from one or two np to five or six sbort-lived males 

 without mouth or stomacb.« 



Lastly we bave tbe ordinary bermapbrodite Cirripedes. Tbiis we 

 bave among tbe Cirripedes ali stages from unisexual forms to complete 

 hermapbrodites. 



I sball proceed to sbow tbat witbin tbe mucb narrower limits of 

 tbe genus Myzostoma , we bave tbe same passage from tbe unisexual 

 condition to tbe bermapbrodite, or if one will vice versa. My researcbes 

 bad already led me to tbe conclusions regarding tbe sexuality of M. 

 c/labrum detailed in the preceding pages , which conclusions I indeed 

 arrived at about tbe dose of last year 1883, wben in January of tbis 

 year Prof. Graff's most recent paper^ on tbe genus arrived in Naples. 

 Tbis short paper contains a description of a number of very interesting 

 new species, 21 in number — among them those collected by the 

 Challenger Expedition. Most of tbe forms are bermapbrodite, but three 

 forms are especially interesting as being unisexual. These three species 

 are ali cysticolous. M. cijsticolum^ (Graff) is imperfectly bisexual. 

 Tbe female is 2mm in diameter, its body cavity is fiUed with ova and 

 only very scanty rudiments of testes are present, and there areno 

 male sexual apertures. In the small male, which is only 0,8mm 

 in diameter there are only testes and no traces of female sexual open- 

 ings. »Im Männchen .... finden sich bloß die beiden compacten Hoden 

 und keine Spur von weiblichen Geschlecbtsöffnungen.« 



Thus this species is not perfectly unisexual , but when we come to 

 tbe second and tbird of the three species we shall find there no traces 

 of male organs in the female , and thus these two species are perfectly 

 unisexual. In 31. mflator tbe female is 2,2 mm in length and the male 

 0,9 mm. Graff 3 says: »Reste von Hoden bei dem Weibchen dieser 

 und der folgenden Species [M. Murrayi] nicht constatirt.« 



M. Murrayi, tbe tbird and last of tbe three, is very large. The 

 female is 5,5mm in length, tbe male 1,3mm. As stated above this 

 species is perfectly unisexual. Darwin ^ described forms witbin tbe 

 Cirripedia, which showed all stages from tbe unisexual state to the 



1 Bulletin of the Museum of Comp. Zoology. No. 7, XXVI. — Grafp, Ver- 

 zeichnis der von den United States Coast Survey steamers »Hassler« und »Blake« 

 von 1867— 1S79 gesammelten Myzostomiden. 



2 1. c. p. 133. 3 1. c. p. 133. M. c. 



