i go 



THE ORIGIN OF VERTEBRATES 



Ut. Masc. 



Int. Op. 



Ext. Op. 



and a lateral posterior, which covers the first pair of gills, or lung- 

 books, as they are called. In this type (Fig. 77) the genital ducts 

 terminate in a common chamber or uterus, the nature of which will 

 be further considered. 



As has been pointed out by Blanchard, the terminal genital 

 organs of the scorpions and the Pedipalpi vary considerably in the 

 different genera, especially the male genital organs. The general 

 type of structure is the same, and consists in both male and female 

 of vasa deferentia, which come together to form a common chamber 



before the actual opening 

 to the exterior. This com- 

 mon chamber has been 

 called in the female scor- 

 pion the vagina, or in 

 Thelyphonus the uterus. 

 I shall use the latter term, 

 in accordance with Tar- 

 nani's work, and the corre- 

 sponding chamber in the 

 male will be the uterus 

 masculinus. 



A considerable discus- 

 sion has taken place about 

 the method of action of the 

 external genital organs in 

 the members of the scorpion 

 tribe, into which it is hardly 

 necessary to enter here. 

 The evidence points to the 

 conclusion that in all these forms the operculum covers a median 

 single chamber or uterus, into which the genital ducts open on each 

 side, the main channels of emission being provided with a massive 

 chitinous internal framework. We may feel certain that in the old 

 extinct sea-scorpions, Eurypterus, etc., a similar arrangement existed, 

 and that therefore in them also the median portion of the operculum 

 covered a median chamber or uterus composed of the amalgamation 

 of the terminations of the two genital ducts, which were originally 

 separate, as in Limulus. 



The observations of Schmidt, Zittel, and others show that the 



Fig. 77.— Operculum and Following Seg- 

 ments of Male Thelyphonus. 



Opercular segment is marked out by thick black 

 line. Ut. Masc, uterus masculinus ; Int. Op., 

 internal opening of uterus into genital chamber ; 

 Ext. Op., common external opening to genital 

 chamber (Gen. Ch.) and pulmonary chamber. 



