Character and Distribution of the genus Peiigonimus. 483 



to enter upon auy coraparison , further than iu a vciy general way. 

 Tbis much, however, may be said, tbat in P. Jonesii tbe germ-cells 

 evidently mature at a mucb later date in tbe life of tbe medusa tban 

 in P. ciclarifù. In tbe latter tbey may be found, according to Weis- 

 mann at, or shortly prior to, tbe setting free of tbe medusa. »So 

 viel stebt jedenfalls fest, dass die Gescblecbtszelleu bei Perigonhnus 

 erst in der Medusenknospe entsteben kurz vor ibrer Lösung, und zwar 

 aus dem inneren Blatt des Glockenkerns, aus dem Ektoderm des 

 Manubrium.« I bave not been able to demonstrate their presence 

 in P. Jonesii at any stage previous to tbe maturation and liberation 

 of tbe medusa, even in tbe most primitive forms.; thougb careful searcb 

 has been made tbrougb many sections of tbe medusa-buds in various 

 stages of development. In a previous account of tbe development 

 of tbis species^, attention was called to tbe circumstance tbat tbe 

 medusae were kept in aquaria — apparently in bealtby condition for 

 at least a fortnigbt — witbout any appearance of sexual organs ; but 

 it must be said tbat no sections were made of specimens so kept, 

 tbougb careful observations upon stained and mounted specimens failed 

 to sbow any traces of sexual cells. 



It would seem therefore tbat in tbis respect at least, tbere is a 

 rather remarkable diflference as to tbe origin and maturation of tbe 

 sexual cells in tbese two species. But attention sbould be called to 

 the fact tbat Weismann's conclusions were in part based upon sexual 

 Organs fonnd upon medusae taken from tbe »Auftrieb«, and wbose 

 age, and iudeed relations, must therefore be a matter of some doubt 

 I shall hope to be able to secure such additional material as will 

 afford means for certainly establishing tbis point for tbe American 

 species, and at tbe same time for completing an account of its mi- 

 nute structure and development, of which only preliminary notice 

 has so far been given. 



In numbers tbe genus is also an important one, perhaps only 

 tbe Corynidae and Tubularidae including more species. Hincks ^ re- 

 cords 5 distinct species, and adds several which be considers as of 

 doubtful affinities, tbougb tbey are now generally recognized as dis- 

 tinct species. Allman in bis classical monograph recognizes 8 dis- 

 tinct species, and adds two of doubtful character. He adds also an 

 additional species 3, P. multicornis, reported in 1874. 



1 Op. cit. pag. 28. 



2 Op. cit. pag. 89. 



3 Journ. Linn. Soc. London Vol. 12 pag. 2.32. 



