Plate II. 



All the figures represent embryos of Tjalfiella tristoma. All 4°/i. 



Figs. 1—3. Stage I. Fig. i. from the oral side, showing the transverse furrow; 2. side view (from the 

 tentacular plane), showing the costse and tentacle rudiments; 3. from the aboral side 

 showing the aboral organ, the costse and tentacle rudiments. The small, irregularl>- 

 placed spots are probably only artefacts, products of the preservation. 



— 4 — 6. Stage II. 4. from the oral side, 5. .side view (from tentacular plane), 6. from the aboral 



side. The combs have begun to appear. 



— 7. Embryo slightly younger than Figs, i — 3, from the oral side. The transverse furrow is 



quite short, the oral opening being distinct. The aboral side of the specimen figured 

 was as in Fig. 3. 



— 8 — II. Stage III. The fully developed young Cydippid, ready to leave the egg-membrane (but 



found lying within the membrane). 8. seen from the sagittal plane, 9. from above, 10. from 

 the tentacular plane, 11. from the oral side. In fig. 9 are seen the ciliated ridges passing 

 from the sense organ to the costse. The tentacle is rolled up within the tentacle sheath. 



