STINGING-CELLS IN GEASPEDOTE MEDUSA. 783 



Fig. 2. — A transverse section through the same region. 



Fig. 3. — A longitudinal section of the distal part of the manubrium 

 showing the oral battery and a stinging-cell {nem.^) migrating through 

 the endoderm towards it. 



Fig. 4. — A similar section showing a stinging-ceU {nem") making its 

 way through the structureless lamella to the ectoderm. 



PLATE 43. 



Explanation op Lettering. 



c.b. Cavity of the medusa-bud. c.e. Cavity of the entocodon, i . e . 

 subumbrella cavity, c.vi. Cavity of manubrium, ect. Superficial ecto- 

 derm of the developing gonophore. end. Endoderm of the same. ent. 

 Ectoderm of the entocodon. g.c. Gland-cell, i.c.e. Literstitial cell of 

 the endoderm. nem. Small nematocyst. nem.^ Large nematocyst. 

 ti.s. Nutritive sphere of the endoderm. r.p.e. Radial pouch of endo- 

 derm. r.p.e.^ Lateral solid entension of the same, which later forms the 

 endoderm lamella, s.c. Sex-cell, tent.b. Tentacle-bulb. test. Testis. 

 V. Velum. 



Fig. 5. — Longitu.dinal section of an early stage in the formation of the 

 gonophore of Moerisia lyonsi (cf . text, p. 775). 



Fig. 6. — Tangential longitudinal section of a young bud showing the 

 entocodon and a single radial endoderm pouch. 



Fig. 7. — Transverse section of an older gonophore to illustrate the 

 complete independence of the four radial pouches. The entocodon 

 already has a large cavity (subumbrella cavity), and at r.^j.e.^ can be seen 

 the solid extension of the edge of a pouch which later forms the endo- 

 derm lamella. 



Fig. 8. — Radial longitudinal section through a similar (slightly 

 youngei-) bud, showing two radial pouches of endoderm separated by the 

 entocodon. 



Fig. 9. — Tangential longitudinal section of the same medusa-bud ; 

 only a single pouch is shown. 



Fig. 10. — Longitudinal section of an almost completely develoj)ed 

 medusa to show the bulbous swellings at the termination of the radial 

 pouches. 



Fig. 11. — Manubrium of the same medusa under a higher magnifi- 

 cation. 



Fig. 12. — Section through the testis of an adult medusa, part of which 

 has given rise to a stinging-cell battery. 



