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University of California Pnhlications. 



[Zoology 



Allman snggested a number of interpretations for this varia- 

 tion, among them being a possible difference of sex. The cor- 

 bulae of his specimens were empty, so that he could not establish 

 that view. That it was correct, however, seems to be demon- 

 strated by the discovery of similar conditions in several species 

 of Aglaophenia from the California coast. The sexes of the 

 latter were determined without difficulty in each case through 

 the presence of mature gonophores in good condition. There is 

 one difference between Allman 's statement and our observations, 

 however. He found both open and closed corbulae ' ' on one and 

 the same colony." That is never the case in the species which 

 we have examined. It is possible that Allman 's "colony" may 

 have been a close aggregate of two or more colonies of opposite 

 sexes. These aggregates are not rare in our material, but the 

 same stem never bears more than one kind of corbula. 



Fig. 8. Male corbula of A. inconspicua. X 20. 

 Fig. 9. Female corbula of A. inconspicua. X 20. 



In A. diegensis Torrey (figs. 1-3), A. pluma (Linn.) (figs. 

 4, 5), A. struthionides (Murray) (figs. 6, 7), and A. inconspicua 

 Torrey (figs. 8, 9), the corbulae of the two sexes are distin- 

 guished by the same characteristic which distinguishes the sexes 

 in .i. filicula Allman. The female corbulae in all are closed boxes 

 formed by the fusion of contiguous corbular leaflets by their 

 edges. The male corbulae are more or less open, owing to the 



