Vol. 3] Sexual Dimorplnsm in Aglaophewia. 51 



incomplete fusion of contiguous leaflets at their tips. The de- 

 gree of fusion differs slightly among the four species. A. die- 

 gensis approaches A. fiMcula most nearly in this respect. The 

 gaps between the apical halves of adjacent corbular leaflets, 

 prominent in A. pluma, are least noticeable in A. inconspicua. 



It is significant that the closed corbula surrounds the female 

 gonophores. The latter are readily distinguished in all the spe- 

 cies examined. In both sexes the gonophores are sessile sporo- 

 sacs. The regular contour and the central spadix of the ripe 

 male contrast clearly with the more or less irregular contours 

 of the female, with the spadix laterally displaced by the usually 

 single large egg: The embryos develop within the female gono- 

 phores for a time, but reach their characteristic long slender 

 form after they have escaped into the corbular cavity. Here 

 they are retained, well protected, until a rupture of the wall sets 

 them free. 



The female corbulae in the above species have been described 

 as closed. Between the bases of the corbular leaflets, of both 

 males and females, however, are obscure oblique openings left by 

 the incomplete fusion of the leaflets in this region. As figured 

 by Nutting ( :00), the closed corbulae of A. latirostris Nutting, 

 A. gracillima Fewkes and A. calamus Allman are furnished with 

 well defined openings in the same region. 



Associated with these openings in A. struthionides, A. die- 

 gensis, A. pluma, A. inconspicua, and A. octocarpa, are two 

 nematophores, smaller and more closely approximated than the 

 rest. They are borne on the proximal edge of each corbular 

 leaflet and are concealed, under ordinary conditions, by the 

 nematophores on the distal edge of the leaflet next adjoining to- 

 ward the base of the corbula. They are the lowermost of a se- 

 ries of proximal nematophores which are really remains of an 

 originally functional condition. Careful dissection, as Nutting 

 has said, is required to see the others at all. 



Open corbulae have been found previously not only in A. fili- 

 cula, but in A. aperta Nutting and A. apocarpa Allman. In the 

 latter two species, however, open corbulae alone are known and 

 have been regarded as typical for the whole species. Our evi- 

 dence appears to justify the suspicion that they will prove ulti- 



