Plate II. 



All the figures represent embryos of Tjalfiella tristoma. All 4/,. 



Figs. 13- Stage I. Fig. i. from the oral side, showing the transverse furrow; 2. side view (from the 

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

 showing the aboral organ, the costae and tentacle rudiments. The small, irregularly 

 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, n. from the oral side. In fig. 9 are seen the ciliated ridges passing 

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



