THE DEVELOPMENT OF THE EARTH-WORM. 2l9 



great soever may be the difference between the mode of pro- 

 duction and the anatomical and physiological relations of the 

 two alternate generations of Salpa and the gemelliparous de- 

 velopment of Lumbricus trapezoides, it is not possible to fail 

 to see the simie principle ruling in both these forms of de- 

 velopment, Todaro was led to the conclusion that the 

 explanation of the phenomenon is to be sought in the earliest 

 steps of the process of sexual reproduction.^ 



The following considerations may, perhaps, suggest a 

 means, a little difficult, however, in the application, for 

 solving the question definitely. The important labours of 

 Fol^ and of Hertwig^ have rendered it very probable that 

 not only is the introduction of a single spermatozoon into 

 the protoplasm sufficient to establish an orderly and efficient 

 generative movement, but that the presence of more sperma- 

 tozoa, instead of assisting the development, occasions a 

 serious disturbance of the order of the molecular arrange- 

 ments, producing a number of centres of activity, and thus 

 leading to an irregular segmentation, and at last to the com- 

 plete destruction of the embryoplastic material. Now, the 

 thought naturally presents itself, that in some case, the action >S/ 

 of two spermatozoa introduced into an egg of great vitality, 

 regulated by means of special dispositions, might augment 

 instead of turning aside and paralysing the productive force 

 of the Qgg, inducing in it a transformation not, as is usual, 

 into one, but into two perfect embryos, and this might be 

 the case in humbricus trapezoides. 



The fact that each capsule of L. trapezoides produces two 

 worms was known to Duges,^ who also observed and figured 

 a double monster ; and Ratzel and Warschawsky describe a 

 like abnormality in L. agricola. It is a pity that the descrip- 

 tion which these authors give of the first stages of develop- 

 ment is too superficial to allow a precise conception of them 

 to be made.^ 



This double reproduction is exceptional even in the single 

 genus Lumbricus. L. teres follows the ordinary rule, pro- 

 ducing one embryo from an e^^ and no more ; the same holds 

 good, without doubt, for L. ruhellus. 



As the duplicity of the embryos has no influence on the 



1 ' Sopra lo sviluppo e I'anatomia delle Salpe.' Roma, 1875, p. 68, cf. 

 Hatschek " Oa Pedicellina," ' Zeit. fiir Wiss. Zool.,' T. xxix, p. 530. 



- 'Sur le commeuc3ment de I'lienogenie.' Geneve, 1877, p. 25. 



3 ' Morphologisches Jahrbuch,' T. N., 1878, p. 172. 



* 'Annales des Sciences Naturelles,' T. xv, 1828, pp. 331—332. 



^ Loo. cit. The processes described in this work as the first phenomena 

 of development belong, as Kovyfalewsky has justly observed, only to the 

 degeneration of the noa-fecuudated eggs. 



