Geucralions^ Melamorphusis, cCr. 41 



lias already iiiKleigoiic considerable reduction, surely bears 

 witness to the f>eneral striviii<]f after a constantly shorter 

 tacliygony, although, from internal causes of which we are 

 btill ignorant, in tlie case of many lower animals this has not 

 yet advanced so far as direct development. 



As the weightiest objection to my interpretation I shall 

 naturally again have to encounter the views on phylogeny 

 which are held to-day. In the case of the lowest orders 

 among the Tunicata we find direct development : consequently 

 the alternation of generations in the higher Tunicata, which 

 are evidently derived from the former, can only be a secondary 

 acquisition. And likewise in the case also of the hio-her 

 insects, since they are said to be derived from their lower 

 relations which have direct development, "complete"" meta- 

 morphosis can only be of secondary origin. 



In opposition to this line of argument, however, I would 

 call attention to the self-evident truth that in no class of the 

 animal kingdom does there obtain a relation of direct descent 

 between its existing higher and lower orders, and to this rule 

 the Tuuicates and Insects form no exceptions. The ancestral 

 form of the Tunicata was consequently not in all points 

 identical with the Appendicularidie of the present da}', but 

 must at least have had a divergent attribute in common 

 with the higher Tunieates. And thus we may naturally 

 just as well imagine these Archi-Tunicates as in other 

 respects entirely similar to the Appendicularidaj, but with 

 asexual reproduction. A portion of these, the present 

 Appcndicularidas, then branched off to one side quite early, 

 and displayed a very rapid and precocious transition to 

 sexualit}', so that they, perhaps evei^ in consequence of this 

 over-speedy advance to sexual life, subsequently remained 

 stationary at a lower stage of the development of the phylum. 

 On the other hand the majority, while retaining asexual 

 reproduction for a longer period, continued perhaps on that 

 account slowly but nevertheless surely to make progress in their 

 phylogenetic development, until in their case also a conclusion 

 was reached with the attainment of sexuality in the higher 

 orders. Moreover, this phylogeny of varying length was 

 subsequently retained in the ontogeny also. JSince no other 

 material difference any longer existed between the ancestral 

 form with asexual and the present Appendicularidie with 

 sexual reproduction, ontogeny, too, was easily able to proceed 

 to direct development, while the less rapid phylogeny of the 

 higher orders has left its traces in their ontogeny even at the 

 present day. 



Similarly, too, the "typical arehi-normal Insect'^ was, in 



