LIFE AND DEATH. 131 



fluity, and on the other demands the production of a great number 

 of germ-cells 1 . It is certain that the Orthonectides, as at present 

 constituted, cannot have lived in the free condition, and also that 

 their adaptation to parasitism cannot have arisen at the beginning 

 of the phyletic development of Metazoa, because they inhabit star- 

 fishes and Nemertines both relatively highly developed Metazoa. 

 Hence it is, at any rate, doubtful whether the Orthonectides can 

 claim to pass as typical forms of the lowest Heteroplastids, and 

 whether their reproduction can be looked upon - { as typical for the 

 unknown ancestors of all Polyplastids' (1. c., p. 45). If, however, we 

 accept some organism resembling these Orthonectides as the most 

 ancient Heteroplastid, being a free-living organism, it must have 

 had a stomach, and the cells surrounding it must as a whole or in 

 part have possessed the power of digesting ; at any rate, they 

 cannot all have been germ-cells, and therefore it is improbable that 

 death would be the direct result of the extrusion of the germ-cells. 

 Let us now consider the manner in which Gotte has endeavoured 

 to explain the transmission of the cause of death which first 

 appeared in the Orthonectides from these organisms to all later 

 Metazoa, until the very highest forms are reached. Exact proofs 

 of this supposition are unfortunately wanting, and the evidence is 

 confined to the collection of a number of cases in which death and 

 reproduction take place nearly or quite simultaneously. These 

 would prove nothing, even ifjjost hoc were always propter hoc ; and 

 there are, opposed to them, a number of cases in which reproduction 

 and death take place at different times. In obtaining evidence for 

 'the fatal influence of reproduction,' is it possible to point to every 

 case of sudden death after the act of oviposition or fertilization ? 

 These cases occur among many of the higher animals, especially in 

 Insects, and were collected by me in an earlier work 2 . It is 



1 Leuckart finds such a great resemblance between the newly born young of 

 Distoma and the Orthonectides, that he is inclined to believe that the latter are 

 Trematodes, ' which in spite of sexual maturity have not developed further than the 

 embryonic condition of the Distoma' (' Zur Entwicklungsgeschichte des Leberegels,' 

 Zool. Anzeiger, 1881, No. 99). In reference to the Dicyemidae, which resemble the 

 Orthonectides in their manner of living and in their structure, Gegenbaur has stated 

 his opinion that they belong to a ' stage in the development of Platyhelminthes ' 

 (Grundriss d. vergleich. Anatomic). Giard includes both in the 'phylum Vermes,' 

 and regards them as much degenerated by parasitism ; and Whitman the latest inves- 

 tigator of the Dicyemids speaks of them in a similar manner in his excellent work 

 ' Contributions to the Life-history and Classification of Dicyemids' (Leipzig, 1882). 



2 ' Dauer des Lebens ; ' translated as the first essay in this volume. 



K 3 



