NO. 1791. 



SPERM TRANSFER IN DECAPODS— ANDREWS. 



425 



preservation of material would be necessary to decide how far the 

 mass about the sperm was run in against the shell as a liquid or in how 

 far it existed outside the thely- 

 cum as a spermatophore with 

 its walls already formed." 



In a third prawn, Parapenseus 

 constrictus Stimpson, specimens 

 65 mm. long present a thelycum 

 as figured in figure 6. The scales 

 are here evidently an anterior 

 continuation of a transverse 

 plate between the fifth legs. 

 The shelf (S) passing back from 

 between the fourth legs disap- 

 pears under the scales. 



In this figure of the female 

 the right first pleopod is in- 

 cluded to show the minute 

 endopodite. In the male the 



region of the thelvcuin of the ^g- 6-part of ventral side of thorax of para- 



C ^ . . , . PEN^US CONSTRICTUS, SHOWING BASES OF LEGS, ONE 



female is occupied by two ridges : of the first pleopods, and the scales (Sc) and 

 A transverse ridge between the '^"'" ^'^ °" ™^ thelycum. 

 fourth legs in place of the female shelf and a longitudinal ridge, ex- 

 panding as a T-shaped mass, representing the scales of the female. 





■l-fi.-. 



c, ■;■?-:; 



Fig. 7.— Longitxidinal, lateral section of thelycum of Parapen^us constrictus. S, shelf 

 AND Sc, scale; overhanging a branched cavity. 



Returning to the female thelycum, it may be noted that the scales 

 and the shelf are both sparsely covered with short bristle-like setae. 



a Five specimens obtained alive at Montego Bay, Jamaica, Aug. 22, 1910, measured 

 90, 100, 120, 120, 160 mm., and each possessed a well-formed thelycum. The scales 

 ■were translucent enough to show the curved sperm mass under each and soft enough 

 to be readily separated by forceps so that the male might introduce a large spermato- 

 phore. When dissected the sperm was in a bag on each side which had a stiff lat- 

 eral edge and might well be formed in the petasma. The shelf projected into the 

 thelycum as a median and two lateral spines. The sperms were spheroidal, with 

 one stiff process. In one specimen a soft gelatinous mass projected from under the 

 Bcales forward over the shelf some distance into the water. 



