THE REPRODUCTIVE SYSTEM OF E. SUPERBA 



345 



These glands sgl (Plates II-V and Figs. 23 and 25) surround the oviducts od (Fig. 23) 

 in their course through the thoracic cavity and extend into the coxopodites of the last 

 four pairs of thoracic legs, including the last two vestigial pairs seven and eight (Fig. 25). 

 They lie between the gills corresponding to these appendages, below the body wall 

 and the large flexor abdominalis muscles /am, and extend under the ventral nerve-cord, 

 in the region of the genital pores and posterior to them (Fig. 25). 



The oviducts can be traced through the gland masses both by dissection and by the 

 examination of serial sections. Figs. 23 and 25 represent dissections to show their 

 relation to the other parts of the reproductive system, and Plates II-V are photo- 

 micrographs of transverse and longitudinal serial sections through the thorax of an 

 adult female. At the point at which the oviducts leave the ovaries (Plate II, figs. 3 and 4), 

 they are fairly thick-walled with a narrow lumen, but, on reaching the coxopodites of 

 the legs, they widen to form a thin-walled atrium into which the secretion of the glands 

 appears to be poured, to surround the eggs before they are laid (Plate III, figs. 2, 3 and 4). 



Fig. 26. Three views of the thelycuin. a, ventral; b, anterior; c, dorsal, a, anterior opening; 

 c, coxopodite of sixth leg; egp, external genital aperture; p, posterior opening. 



It seems probable that the great flexor abdominalis muscles /aw, which run ventrally 

 in the thorax and abdomen, and which increase markedly in size in the region of the 

 last thoracic leg, assist in the expulsion of the eggs (Fig. 25). The coxal muscles cm 

 may also operate in the same way (Fig. 25 and Plates II-V). 



The external genital pores egp (Fig. 25) are transverse slits surrounded by thick 

 lips, and they open into the narrow space between the coxopodites and the ventral 

 body wall (Plate IV, fig. i and Plate V, figs, i, 3 and 4). Sars (1885) and Chun (1896) 

 described the genital pores in Euphmisia and Stylocheiron as being unpaired apertures 

 on the ventral surface of the sixth thoracic segment. Zimmer (1913) found them on 

 the basal j oint of the sixth pair of thoracic legs . Raab ( 1 9 1 5 ) , working on Meganyctiphanes 

 and Etiphamia krohnii, states that they do not lie on the basal joints, but next to two 

 plates (thelycum) connected to the legs close to the middle line. It will be seen from 

 Fig. 25 and Plates II-V that in E. superba they lie on the coxopodites. 



Immediately between the genital pores egp is the posterior opening/) of the thelycum th 

 (Fig. 26c), a pouch formed partly by two wing-like expansions of the coxopodites and 

 partly by an outgrowth from the sternal wall (Plate V, fig. 3). These three plates are 

 fused posteriorly and ventrally, but are wide open anteriorly forming the mouth of the 



