THE NEW GENEALOGICAL TREE 387 



during the ontogenetic processes— even in groups which 

 are otherwise obviously closely related, it becomes evident 

 that it is better not to use the conditions of the coeloms 

 as a basis for classification. Zoologists should therefore avoid 

 such classifications as the Coelomata (because of the unten- 

 ability of their counterpart, the "Coelenterata"), the Acoelom- 

 ata, the Pseudocoelomata, etc. As an example, we mention 

 here the lower "Coelomata" or the "Bilateria." The coelom 

 cavities can be found as early as in the Turbellaria which we 

 consider as the earliest Eumetazoa. These cavities occur in 

 three forms if we do not take into consideration the digestive 

 cavity. First of all we can frequently find a whole system of 

 canals, often with a vesicle at its extreme end; this is the so- 

 called protonephridium which functions as an emunctory- 

 excretory organ. We derive this nephrocoele from the pulsat- 

 ing vacuoles of Protozoa. 



There have been some zoologists who would like to con- 

 sider this nephrocoele as an initial state for the evolution of 

 the "genuine coelom" (the perigastrocoele; the nephrocoele 

 theory which was proposed by Faussek). This is completely 

 wrong because we can find this nephrocoele preserved as such 

 up to the very end of evolution; it is quite natural that during 

 the evolution it had been variously changed, especially after the 

 appearance of the perigastrocoele. This nephrocoele was 

 occasionally lost in the permanently sessile types whose size 

 had been secondarily strongly diminished as has already been 

 mentioned. In some other cases we find this nephrocoele 

 changed beyond recognition (e.g. in numerous Arthropoda 

 with the so-called mixocoele). Cases are also known where 

 a combination of the nephrocoele with the perigastrocoele 

 (which had developed much later), or with other coelom 

 cavities (e.g. the gonocoele) have been observed. 



The second coelom which appeared quite early during the 

 phylogeny of the Eumetazoa is the gonocoele. It evolved 

 completely independently and without any phyletic connec- 

 tion with the protozoan ancestors of the Eumetazoa. Earlier 



