HYDRAHLE : HYDRA. 133 



or five days after its separation, the whole produce of a month was 

 prodigious.* 



" No sooner is a young one furnished with arms, than it seizes and 

 devours worms with all possible eagerness ; nor is it an unusual 

 thing to behold the young one and the old one struggling for, and 

 gorging, different ends of the same worm together. Before the arms 

 come out, and even some time afterwards, a communication continues 

 between the bodies of the old and young, as appears beyond dispute 

 by the swelling of either when the other is fed.f But a little before 

 the young one separates, when its tail-end begins to look white, 

 transparent, and slender, the passage between them, I believe, is 

 closed. And when the young one comes away, there remains not 

 the least mark where it had been protruded." "After a young 

 polype once gets all its arms, it alters indeed in size, but neither 

 appears to shift its skin, nor undergo any of the changes most other 

 insects do."J 



Instead of buds or little protuberances, the body sometimes pushes 

 forth single tentacula scattered irregularly over it, and these tenta- 

 cula can be metamorphosed into perfect polypes, the base swelling 

 out to become the body, which again soon shoots out additional ten- 

 tacula to the requisite number ! 



This is a mode of generation which the term viviparous does not 

 correctly embrace, unless we give to that word a signification so 

 extensive as to include all generations which are not oviparous : it is 

 an example of equivocal, or what some foreign physiologists deno- 

 minate, the generation by the individualisation of a tissue previously 

 or already organised, || and seems to be the usual way of propaga- 

 tion among the Hydrae during the summer months. But in autumn 

 the Hydra generates internal oviform gemmules, which, extruded 



* Mem. pour 1'Hist. des Polypes, 174-5. Also Baker, lib. s. cit. 53-4. 



t By some clever dissections, Trembley demonstrated the reality of this commu- 

 nication. Mem. 161-2. 



+ Baker, lib. s. cit. 50. Baker ut cit. 110-11 ; 121-3. 



|| " La generation ii'est pas pour cela spontanee ; une generation spontanee doit etre 

 la production d'un etre organise de toutes pieces, lorsque des elemens inorganiques 

 se reuniront pour produire un animal, une plante. Cette generation est impossible, 

 et n'a jamais lieu. Une generation equivoque est celle ou des tissus organises preala- 

 blement par un etre deja pourvu de vie, s'individualisent, c'est-a-dire se separent de 

 la masse commune et participent encore, apres cette separation, de l'tat dynamique 

 de la masse, c'est-a-dire de sa vie, mais, a son propre profit. C'est ainsi qu'un tissu 

 produit un Entozoaire. C'est de la vie coutinuee." Ch. Morren in Ann. des Sc. 

 Nat. vi. p. 90. 



