58 C. 0. Whitman 



3. Both female forms are oviparous, and produce eggs that are 

 alike in size and general characters : but the mature eggs of the cylin- 

 drical female are expelled from the mother, and are completely 

 independeut of one another; while those of the fiat female are never 

 expelled ; but remain united by a granular substanee , in small masses 

 that are nothing but fragments of the mother. 



4. In both sexes the whole central cell (»globe endodermique pri- 

 mitif«) breaks up, before the dose of the blastopore, into cells from 

 which arise later the muscular layer and the numerous germ-cells. 



5 . Both of the adult female forms are supposed to be able to escape 

 from the host in which they have developed and matured, and to swim 

 free until they meet with a new host into which they may penetrate. 



(i. Arri ved in the new host , the cylindrical female ends its 

 existence in the act of expelling its eggs; the fiat female ends by 

 breaking up into fragments which become so many sacs (»Plasmodium- 

 schläuche«, Metschnikoff) each inclosiug a number of ova. 



7. It is probable that the eggs of the cylindrical female are 

 fecundated at the time of expulsion, »les spermatozoides pouvant étre 

 amenés par l'eau« ; but it is left entirely undecided whether the eggs of 

 the fiat female are fecundated, or develop parthenogenetically. 



As to the Dicyemids , nothing in the nature of fecuudation has yet 

 been discovered, and presumably nothing of the kind occurs in the 

 monogenie individuals. In the case of the diphy genie individuals, there 

 is perhaps some reason to suspect that fecundation introduces one of 

 the two modes of reproduction. The chief ground for the suspicion is, 

 however , the absence of any other equally plausible explanation of the 

 origin of those peculiarities which distinguish Khombogenic repro- 

 duction. 



In bis earlier paper, Van Beneden says, — »J'ignore également si 

 la reproduction des Dicyémides se fait exclusivement par voie agame ou 

 si la production des embryons de Fune ou -de l'autre forme est précédée 

 d'une fécondation véritable J'ai observé quelques fa its qui 

 me font pencher vers cette dernière alternative. Peut- 

 étre la production des Infusoriformes est- elle précédée de la fusion 

 d'une cellule ectodermique avec la cellule endodermique de l'embryon 

 vermiforme.« (1, p. 69.) What these facts are is not stated. Per- 

 haps the supposed variability in the number of the ectodermal cells in 

 the diphygenic individuals was at the bottoni of this conjectnre. 



In this connection an Observation may be mentioned , to which I 

 should not hesitate to attributo considerable importance, had it been 



