+-----------------+---------+---------+---------+---------+---------+ | Deilephila. | Ontogeny| Ontogeny| Ontogeny| Ontogeny| Ontogeny| | | Stage 1.| Stage 2.| Stage 3.| Stage 4.| Stage 5.| +-----------------+---------+---------+---------+---------+---------+ | 1. Hippophaës | ? | ? | ? | III. | III.-IV.| | 2. Zygophylli | ? | ? | ? | ? | III.-IV.| | 3. Lineata | ? | ? | ? | ? | IV. | | 4. Livornica | ? | ? | ? | IV. | V. | | 5. Galii | ? | ? | IV. | V. | VI. | | 6. Vespertilio | ? | II. (?) | IV. | V. | VI. | | 7. Mauritanica | ? | ? | ? | ? | VI. | | 8. Dahlii | I. | ? | VI. | VII. | VII. | | 9. Euphorbiæ | I. | V. | VI. | VII. | VII. | | 10. Nicæa | ? | ? | VII. | VII. | VII. | +-----------------+---------+---------+---------+---------+---------+ From this very incomplete table we perceive that, in certain instances, the stages can be represented as a continuous series of phyletic steps, as in the case of _D. Galii_; that in others certain steps may be omitted, as with _D. Euphorbiæ_, in which grade I. of stage 1 is immediately followed by grade V. in stage 2. In reality the gap caused by this omission is still greater than would appear, as grade V. is only indicated, and not actually reached, the subdorsal not being present as a sharply-defined line, but only as a faint stripe. The suppression of phyletic steps increases with the advancement in phyletic development. The higher the step to which a species finally attains, the greater is the tendency of the initial stages to be compressed, or omitted altogether. From what has thus far been seen with respect to the development of _D. Hippophaës_, there may be drawn what to me appears to be a very important conclusion, viz. that the ring-spots of _Deilephila_ first originated on the segment bearing the caudal horn, and were then gradually transferred as secondary spots to the preceding segments. Complete certainty would be given to this conclusion by a knowledge of the young forms of other phyletically retarded species, especially those of the American _D. Lineata_, and perhaps also those of _Zygophylli_ and _Livornica_. The few observations on the development of _D. Galii_ already recorded give support to this view, since the absence of ring-spots on the three front segments in the young caterpillar (one instance), or their less perfect formation on these segments (second instance), indicates a forward transference of the spots.