UNIVERSITY OF CALIFORNIA PUBLICATIONS 

 ZOOLOGY 



Vol. 3, No. 4, pp. 47-52, text figures 9 April 17, 1906 



CONTRIBUTIONS FROM THE LABORATORY 



OF THE 



MARIME BIOLOGICAL ASSOCIATION OF SAN DIEGO. 



XI. 

 SEXUAL DIMORPHISM IN AGLAOPHENIA. 



BY 

 HARRY BEAL TORRE Y and ANN MARTIN. 



Sexual dimorphism may be expressed in hydroids by the' 

 structure of the gonophores and of the gonangia, as is well known 

 to students of the group. Besides the slight differences in con- 

 tour which the different sexual elements produce at ripeness in 

 the gonophores of Tubtilaria Crocea, for instance, there are con- 

 stant differences in the form of the flattened processes which 

 represent the tentacles in both sexes (Torrey, :02, p. 43). The 

 female gonophores of T. ynarina (ibid., p. 46) differ still more 

 widely from the males. The male gonangia of Campanularia 

 pacifica {ibid., p. 53) are somewhat more slender than the female 

 gonangia, and the same is true in Plumularia sctacea and other 

 species. 



It is not generally known, however, that a similar dimorph- 

 ism may be exhibited by the modified branches or corbulae which 

 surround and protect the gonophores in the Plumularian genus 

 Aglaophenia. Corbulae bear to gonangia the same relation that 

 gonangia bear to gonophores. They are receptacles which may 

 enclose receptacles, in other words. Modifications of their struc- 

 ture in accordance with their sex, therefore, signify more pro- 

 found changes in the colony than would appear in gonangia or 

 gonophores alone. 



