I 



Dr. C. Chun on the Siphonophora. 163 



simple organization, which is reflected in the simple biological 

 conditions, but also upon its embryonic development. If it 

 were a retrograde Siphonophore, we might expect that, as in 

 the case of the larvae of the Physophoridse, larval organs 

 would make their appearance, to be afterwards thrown off or 

 replaced by definitive structures. Just on the contrary, the 

 embryonic development of Monophyes primordialis presents a 

 simple course, such as the other Siphonophora no longer dis- 

 play. A few days suffice for the conversion of the fecundated 

 ovum directly into the fully developed animal. Finally, we 

 have in favour of its primitive organization the circumstance 

 that all the Calycophoridse, in their development, pass througl 

 a stage which recapitulates, even in its details, the structure 

 of Monophyes primordialis. Monophyes primordialis is the 

 stem form of the Siphonophora. So far as we at present know 

 the embryonic development of the Calycophoridae, it follows a 

 course almost identical with that of Monophyes primordialis. 

 Throughout, the bud for a nectocalyx is first of all established 

 on the germ, and then one for the tentacle. A larva is formed 

 which sometimes is delusively like the Monophyes. Even 

 external characters, such as the cap-like form, are so exactly 

 reproduced, that one might actually take the figure that Met- 

 schnikoff gives of the larva of Epibulia (Galeolaria) auran- 

 tiaca (Zeitschr. f. wiss. Zool. Bd. xxiv. Taf. vii. fig. 14) for 

 a representation of our Monophyes. 



If we now examine more carefully the stage of Epibulia 

 just mentioned, we are struck in it by a further complication, 

 which engages our interest. Thus, just as the calyx of the 

 Muggicea is established at the base of the stem of Monophyes J 

 there is exactly at the same spot in the larva of Epibulia the 

 bud for a second nectocalyx. But is this destined to separate 

 from the first calyx on arriving at maturity (which, judgin_ 

 from the opposite position of the apertures of the nectocalyces, 

 appears not improbable) ? or does it represent the foundation 

 of the second Diphyid calyx ? In one word, do the Diphyidse 

 also possess three generations, or do they represent more 

 highly developed Monophyida3, in which two free generations 

 are contracted into one ? Further investigation must furnish 

 information upon this point ; nevertheless it is to be regarded 

 as an advantage if we are now able to indicate the time and 

 place at which a third generation might occur. 



From the preceding statements it must be sufficiently clear 

 that the Monophyida3 show the nearest relationship to the 

 Calycophoridae. We may indeed regard them as the lowest 

 of the Calycophoridse, and should best divide this order into 

 three families : — the Monophyidae, with a single nectocalyx ; 







