218 SUMMARY OF CURRENT RESEARCHES RELATING TO 



2. Embryo with the bud-rudiments of the nectocalyx and tentacle. 



3. M. primordialis. 4. Muggicea hocUi, and 5. Eudoxia eschscholtzii. 

 This cyclical development appears to the author to have a close 

 relation to locomotion. 



Where numerous energetically acting nectocalyces occur, as 

 among the Polyphyidte (Eippopodius) and Physophoridfe, the sexual 

 animals remain sessile and often degenerate into medusoid gemmae. 

 Where only one (Monophyidaj) or two nectocalyces (Diphyidae) pro- 

 duced a comparatively feeble locomotion, the diffusion of the species 

 is provided for by the remarkable process of Eudoxia-iormation. 

 Nay, it may happen, as shown in the case of Monophyes primor- 

 dialis, that the first nectocalyx is replaced by a second hetero- 

 morphous one, which is better fitted to carry along the long trailing 

 stem with the Eudoxia-clustevs. From the primitive organization of 

 this Monophyes the life -history of the species therefore appears to be 

 spread over three generations, proceeding one from the other. 

 Lastly, if, as in the most highly organized Siphonophora the Pneu- 

 matophoridfe and Discoidae, the locomotive organs are wanting, the 

 locomotion takes place only passively, the diffusion of the species is 

 rendered possible by the sexual animals being rendered motile. This 

 is an alternation of generations that intervenes, as an element of poly- 

 morphism, in the course of development of the Siphonophora, and 

 indeed of their highest representatives, in this fashion, that on a 

 polymorphic nurse-generation anthomedusaa are produced by gem- 

 mation, either females alone (Pneumatophoridae), or males and females 

 (Discoidfe), which only attain sexual maturity after their separation. 



Ccelenterata of the Southern Seas.*— K. v. Lendenfeld gives an 

 elaborate account of Cyanea annaslcala, a new species very abundant 

 on the southern shores of Australia ; in a careful table the differences 

 of the several species of the genus are pointed out, the relation of the 

 breadth of the umbrella to its cavity, and of the former to the breadth 

 of the central stomach, the form of the ephyral lobes, the colour of 

 the umbrella, of the genital organs, and of the " mouth-arms," and 

 the diameter of the umbrella, being the points that are taken for 

 comparison. 



Histological examination shows that but few kinds of cells take part 

 in the formation of the animal ; not to speak of the great agreement 

 presented by different tracts of the ectoderm, we may note the equal 

 distribution of glandular and flagellated cells in the gastro-vascular 

 cavity. All the sensory cells appear to have the same structure ; 

 more striking differences are to be detected between the various 

 ganglionic cells, but this may be largely due to a want of complete 

 information regarding them. 



In addition to the rare, exumbral, palingenetic, epithelio-muscular 

 cells there are also transversely striated sub-epithelial, and smooth 

 intra-epithelial muscle-cells. The greatest differences appear to be 

 presented by the structures which are known as supporting or covering 

 cells, for these may be ciliated or not ciliated, flat or cylindrical, 



* Zcitschr. f. Wiss. Zool., xxxvii. (1882) pp. 465-553 (7 pis.). 



