Fig. 7. — Radial section through the entire Medusa five times the natural size (semi- 

 diagramatic). ug The solid gelatinous umbrella lens, t Tentacles, tv Tentacle roots. 

 ec Horizontal coronal furrow of the umbrella. Im Gelatinous collar lobes, oo Otoporpse. 

 v Velum, cf Festoon canal, sm Testes, sc Gastral cavity of the testis, yc Central 

 gastral cavity, ga (Esophagus, a Oral opening, dg Endoderm of the subumbral 

 gastral wall, qg Ectodern of the subumbral gastral wall. 



Fig. 8. — Exumbral view of the entire Medusa (from below), four times the natural 

 size. In the left half of the figure the umbrella lens is spead out flat, and the umbrella 

 lobes turned inwards (in their natural position), whilst in the right half the umbrella 

 lens is strongly contracted and the collar lobes spread out flat (by artificial pressure). 

 We see the strong radial ribs of the exumbrella which pass from the central lens on to 

 the peripheric collar lobes. 



Fig. 9. — Subumbral view of the entire Medusa (from below), four times the natural 

 size. In the right half of the figure the greater part of the umbrella is hidden by the 

 broad folded velum (v) and by the collar lobes which are turned inwards (/to), whilst 

 these are removed by a horizontal section in the left half. By this section the testes 

 (sm) are halved and their cavity opened ; we see how they lie protected by the lobe 

 cavities (hi) and run out from the peripheric walls of the shallow stomach whose 

 subumbral wall (gw) is laid in deep folds, g Bottom of the shallow gastral cavity. 

 am Margin of the mouth. 



Fig. 10. — A portion of the distal part of a tentacle, moderately enlarged, q 

 Ectoderm cells, n Spheroidal nematocysts of the ectoderm cells, to Longitudinal 

 muscular fibres, z Supporting plate. 



Fig. 11.— A similar portion of the tentacle in longitudinal section, moderately 

 enlarged. Letters as in fig. 10. dz Chordal cells of the endoderm. yn Central nuclei 

 of the chordal cells (in the axis of the tentacle). 



Fig. 12.— Radial section through the umbrella margin, greatly enlarged, v Velum. 

 vu Subumbral epithelium of the velum, mv Circular muscles of the velum (in trans- 

 verse section), zv Supporting lamella of the velum, ve Exumbral epithelial of the 

 velum, oh Auditory club. 61 Otolites (in which a nucleus, tinged red, is visible after 

 treatment with acetic acid and carmine), oh Auditory hairs, nc Urticating ring of the 

 umbrella margin, re Dorsal nerve ring (in transverse section), re" Ventral nerve ring. 

 oo Otoporpa. tig Gelatinous substance of the umbrella. vf Elastic fibres in the 

 gelatinous substance, cf Distal part of the festoon canal (in transverse section), yc 

 Lobe on the lower margin of the festoon canal, du Umbral endoderm epithelium, dw 

 Subumbral endoderm epithelium of the festoon canal, zw Supporting lamella of the 

 subumbrella. mw Circular muscular layer of the subumbrella, qw Ectoderm epithelium 

 of the subumbrella. 



