REPORT ON THE KERATOSA. 85 



was a time in Zoology when the external shape of the animals was considered quite 

 sufficient for descriptive purposes ; this period was followed Ijy the period of, so to 

 speak, anatomical character, naturalists discovered a new source of systematic characters 

 in Comparative Anatomy, and believed its help to be sufficient for deciding the most 

 complicated phylogenetic questions ; the apparent success was so great that this conviction 

 finds its echo in papers of very recent date — as for instance in v. Jhering's Monograph 

 on the Mollusea. The time came, however, when zoologists became aware that their 

 anatomical hopes were but illusions, and the word Comparative Embryology became 

 the watchword of the day. That this department of Zoology also has not justified the 

 hopes based upon it is but too well known, and the modern watchword is Comparative 

 Physiology. Whether this study, at the present time in its infancy, wQl justify what 

 it promises, will be seen later ; on the whole, it is clear that in most cases not this 

 alone but all branches of Zoology together will give us the answers we require ; but in 

 instances like that concerning the Keratosa, where almost all other lines of research are 

 of no avail, this new science may be particularly welcome. The possibility of a 

 disappointment is of course not excluded, and therefore further purely systematic papers 

 on the Keratosa are of course very desirable. It would he, however, still more desirable 

 that Science, hand in hand -^dth this, would follow up also another way, that, namely, of 

 Comparative Physiology. This is the immediate task to be executed, and in the case of 

 spougiologists residing near the sea-shore it is very easily realisable. 



