36 EMBRYOLOGICAL MONOGRAPHS. 



Tliis layer is an cnoiinous growth of the layer designated by the letters mu. in figure 4. cil' Cilia at the 

 autinal pole. or. Mouth, ta. Tentacle. At A A.^ /i 6.* begin to arise sacs, which later develop into the 

 circulatory-tube system. The tube h l.^ is best marked of these. It A.', It /».- liemains of the original large 

 cells. 



6. Sexually mature, " Cydippe-formed larva," of Cliiaja (Eticharis). At the peripheral extremity of the eight 

 tubes (itdr. tb.) are swollen cavities, filled with sexual products. These lie just beneath the rows of combs 

 or vibratile llappers. adr. tb. Adradial tube, ultimate division of the chyniiferoiis tubes, which extend to 

 a meridional tube below the rows of flappers, ya. Stomach, (ja. tb. A chymiferous tube, in this .stage 

 ending blindly in the bell-walls, and called the stomach tube from its relation in position to the stomach. 

 i. r.tb. Internal radial tube. There are four of these which arise from the base of the funnel and each 

 divides into two adradial tubes (iidr. tb.). n.->. m.5 Nerves. sph. tb. Tube of the funnel, which spi'eads 

 itself out at the upper jiole {.tpli. tb. ) under the nerve centre {tie] Above tlie nerve centre is the otoeyst 

 with its otoliths. 



7 A larva at about the same stage, seen in a plane at right angles to the last, ga: Stomach, here seen in pro- 

 tile, adr. tb. Adradial tube. ga. tb. Stomach tube arising from the funnel (Spit..), i.r.lb. Intcinal 

 radial tube, n.^, «.3 Nerves, n.c. Nervous centre, ta. Tentacle, ta. tb. A tube, wdiicli passes directly 

 to the tentacle from the funnel, tb.^ A blindly ending, meridional tube under a row of vibratile flappers. 

 T).* Row of llappers. lb. Rudimentary lobes. 



8. View of a Cydippe-like larva of Cliittja (Eacliaris) from the actinal pole. adr. tb. Adradial tube, cx.,^ cx.'^ 



E.xcretionary (?) opening, gn. Stomach, n. Nerve. tt.-/ft.8 Chymiferovis tubes, pcr.cn. Canal arising 

 from the base of the funnel before its division into the interradial tubes, ta. Tentacle. 



9. Somewhat older larva from the actinal pole, in which the chymiferous tubes have joined in the bell-walls. 



adr. tb. Adradial tube, aur.'-aur.-^ Auricles, ex. I. tb. Tube skirting the lobe of the body, outside the 

 internal tube (il. tb.). ga. Stomach, ga. sell. Magengefassschenkcl. (ja. tb. Gastric tube seen in 

 section, i.r.lb. Internal radial tube. ^rt. Tentacle. j.i-;.M'oint of bifurcation of the tube which skirts 

 the auricle. 



10. The same -seen from the side. adr. tb. Adradrial tube, aur.'^, aur.^ Auricles, ex.1, tb. External tube of 



the body lobe. ga. Stomach, ga. sck. " Magengefassschenkcl." gaw. Sac-like apiiendage to the stom- 

 ach, i. r. tb. Internal radial tube. lb. Body lobe. mg. to. Medial gelatinous elevation near the otoeyst. 

 m. Nerve, ocij. Otoeyst. ta. Tentacle, ta. tb. Tentacular tube, y.^, 1/.^ Inner wall of the body lobe, 

 seen in profdc. tj.^-ij." Hows ol vibratile flappers. 



n-1". Development of Cc.t^HS Veneris. 



11. Young larva of Ce.itus, seen from one side. ga. Stomach, gn. lb. Tubes one on each side of the stomach. 



«.'-».• Nerves, or. Mouth, spit. tb. Tube of the funnel, tb.'-tb.* Chymiferous tubes, -q. Vibratile 

 flapper. 



12. View of the "Cydippe-formed larva" from the actinal pole. ga. Stomach, ga. tb. Stomach tube. i.r. lb. 



Internal radial tube. ».'-)(.* Nerves, inti. Muscles, ol. Otolith, pcr.cn. First division of the chymif- 

 erous tubes, ta. Tentacle, tb.^-tb.^ Chymiferous tubes. 

 1.3. Still older larva ("Cydippe form"), ga. tb. Stomach chymiferous tubes. mil. ere. Circular muscles. 

 7!..i-».* Nerves, ocy. Otoeyst. or. Mouth, sjyh. Funnel. .<!ph. tb. Tube of the funnel, ta. Tentacle. 

 tb.^-tb.* Chymiferous tubes below the flappers. These have begun to extend downward, but in this stage 

 are blind ending. 



14. Larva of "Cydippe fonn" in which the tubes (tb.) have grown downward towards the oral pole. (View at 



right angles to fig. 13. ) 



adr. tb. Adradial tube. ga. Stomach, ga. tb. Gastric tube. ga. en. Beginning of a bifurcation of tlie 

 extremity of the gastric tube. n. c. 'Nervous centre, sph. Funnel, ta. Tentacle, sph. tb. Tube pass- 

 ing from the funnel to the otoeyst. tb., tb.^-tb.^ Chymiferous tubes, extending mcridionally in the bell- 

 walls. 7;.^, t;." Vibratile flappers. 



15. Ohler larva than that known as the "Cydippe form "(seen in the same plane as fig. 14). ga. Stomach, ga. tb. 



Gastric tulie. ga. Sac-like apiiendage to the stomach, w.gw. Gelatinous elevation near the otoeyst. 

 n. Nerve, ocy. otoeyst. tb.^ Chymiferous tube formed by the junction of two opposite tubes (tb., and 

 tb.^, fig. 14). tb.*, tb.^ Two chymiferous tubes. 



16. An older stage in the development in which the chymiferons tubes (tb.*, tb.^) have joined tb.^ at x.-, x.^ 



ga. Stomach, i.r.tb. Internal radial tube. sph. tb. Tube of the funnel. 



17. Older embryo, in which the larva has become more elongated and band-shaped. 



18, in, Tltni- paradoxa, Chun. 



18. Larva (?) of Lampctia pancerina, Chun, with single tentacle (view showing the tentacle on one side). 



ga. Stomach, lie. Nervous centre. sch. Tentacular sheath. -n.^i).* Kow^s of vibratile flapjiers. 

 tb.\ tb.* chymiferous tubes under flajipcrs t;.^ and >).^ 



