20 THE VOYAGE OF H.M.S. CHALLENGER. 



GONOSTYLES or REPRODUCTIVE STALKS. 



{Blastostyles, Gonoblastidia, Gonodendra, Klinozooids.) 



The gouophores or the medusiform "reproductive persons" of the Siphonophoraa 

 sometimes develop directly on the stem, that is as buds on the gastral wall of the 

 primary siphon. Such is the case in many monogastric Siphonophorse, and in several 

 poly gastric forms {e.g., in Agalmidse) with broken-up cormidia. Much more frequently the 

 buds arise from the stomach-wall of secondary polypoid persons, for which we shall use 

 Allman's title of Gonostyles or Blastostyles. These sacs are usually mouthless, and are 

 described as " tasters," but are better designated sexual palpons. Sometimes (in the 

 Porpitidse and Velellidas) these gonopalpons possess a terminal mouth, and may then be 

 called sexual siphons. These sacs frequently branch in a very marked tree-like fashion, 

 so that the numerous gonophores attached to them form large clustered masses 

 {reproductive-trees, gonodendra). From a physiological point of view the gonostyles 

 are distinguished both from the palpons and from the siphons very essentially in this, 

 that their sole function is the production of gonophores. From a morphological point 

 of view they may be regarded as sterile Polypo-persons, which are related to their 

 gonophore buds, as the Hydropolyp stock to its medusoid buds (poly-person theory). 

 In this case the succession of generations (strophogencsis) would replace the original 

 alteruation of generations ^metagenesis). According to the poly-organ theory, on the 

 other hand, each gonostyle is only to be regarded as an organ, corresponding to a 

 Medusa-manubrium, from which sexual medusoid persons of the next generation arise by 

 budding. 



GONOPHORES or REPRODUCTIVE PERSONS. 



{Sexual- Medusoids, Gonozooids. ) 



Among all parts of the Siphonophoral organism, the gonophores are always those 

 members which most distinctly preserve the original character of the medusoid person. 

 The two principal organs, the umbrella and the manubrium, are always present. In the 

 wall of the latter the generative products arise. But only in the Disconectse (and 

 perhaps in a number of Cystonectse) does the oral aperture of the manubrium appear to 

 break through; in the others it remains closed. The reproductive cells arise in both 

 sexes of the Siphonanthse from the entire surface of the manubrium (as in the Codonidaj), 

 and indeed from the exoderm. The umbrella of the gonophores has the velum and 

 the circular canal of the # umbrellar margin usually well preserved, and the same is true 



