Legend to Diagram of a young Physonect Colony 



A. The whole colony, showing the nectosome and the siphosome with five cormidia. 



A'. This shows that the siphosome has been deliberately twisted to bring the ventral meridian to which the buds are attached 

 from the underside (opposite to that of the nectosome) over to the left for the convenience of the artist. 



B. Enlarged diagram of the nectosome to show (i) the budding zone of the nectophores, and (ii) how the muscular 

 lamellae of the nectophores all arise in one meridian (dorsal) but bend alternately to left and right. 



C. The stem in the region of a blastostyle to show the budding of the male gonophores, a palpon and two of the bracteal 

 lamellae. 



D. Enlarged diagram of the primary terminal gastrozooid. 



The pneumatophore, Pn., stem, St., and terminal gastrozooid, Gz. 1 , represent the original polypoid oozooid. The nectosome 

 gives rise to asexual medusa-buds, and the siphosome to both polyp- and medusa-buds, so that the whole animal may be 

 called a floating bud-colony, as suggested by Garstang (1946). The bracts, Br., are probably neither polyp- nor medusa-buds, 

 but are possibly homologous either with larval actinuloid tentacles, or with larval or adult appendages which have arisen 

 de novo. 



The nectosome with its apical organ — not a medusoid bud, but an air-secreting and air-releasing float (pneumatophore, Pn.) 

 — carries only the propelling nectophores, N. (asexual medusae). The pneumatophore together with the budding-zone for 

 nectophores, which in the larval stage originated on one side of it (Fig. 3), grows upwards (aborally) from the nodal 

 point of minimum growth X. 



The siphosome grows downwards (orally) from the same nodal point X. It consists in the juvenile stage illustrated, of five 

 cormidia or groups of buds, which originated in the larval stage on the side of the pneumatophore opposite to that which gave 

 rise to the budding zone of the nectophores (Fig. 3). The first formed gastrozooid (protozooid) Gz. 1 , with its ring of palpons 

 bearing simple tentacles (palpacles, Pal.) together with a reduced secondary gastrozooid, Gz.(rd.), which bears a less highly 

 elaborate 'larval tentacle', forms the terminal part of the oldest cormidium, and is surrounded by a whorl of larger bracts of 

 larval origin. Four successively younger cormidia can be seen between this and the siphosomal budding-zone or blastocrene, 

 Blcr. 



Each cormidium consists of: 



(1) A distal gastrozooid with branched tentacle, surrounded by 



(2) A ring of bracts and palpons, the latter provided each with a simple tentacle and increasing in number with age. 



(3) Several ventro-lateral rows of bracts. 



(4) A number of intermediate palpons without palpacles, which increase in number with age. 



(5) A number of male medusae (gonophores, androphores), Go. 3, which become separated with age from their budding points 



(blastostyles), and lastly 



(6) A grape-like bunch of female medusae (gonophores, gynophores) Go. ?, which arises from the base of a gonopalpon at the 



proximal end of the cormidium. 

 A tentative analysis of the arrangement of palpons and gonophores in successive cormidia suggests that there is a separate 

 growth-gradient in each cormidium and that new palpons and male gonophores are budded off at several loci, characteristic 

 for each species. The order of the development of successive cormidia is indicated in the diagram by numerals added to the 

 symbols, the explanation of which is as follows : 



Symbol Explanation 



^41,2,3,4 The fi rst ser i es f g as tric palpons, associated with Gz. 1 , Gz. 2 , etc., the first palpons to appear. 



5 1,2,3,4 Intermediate palpons, the second series of palpons to appear. 



(71,2,3 Intermediate palpons, 3rd series of palpons to appear. 



D. lt2 ' 3 Intermediate palpons, 4th series of palpons to appear. 



E. 1 - 2 Intermediate palpons, 5th series of palpons to appear. 



F. 1,2 Intermediate palpons, 6th series of palpons to appear. 



G. 1 Intermediate palpons, 7th series of palpons to appear. 



B.br. Bracteal bud. 



Bl.cr. Blastocrene (budding-zone of siphosome). 



Bl.st. Blastostyle (gonodendron), a bud from the oozooid from which the gonophores bud. 



Br. Bract. 



Br. lam. Bracteal lamella. 



C.br. Bracteal canal. 



