456 



body. Such individuals are obviously protandric and recall the condi- 

 tion described byMontgomery^ for Stichosiemma. 



In the hermaphroditic forms which give rise to embryos within the 

 body it would seem that the body tissues would be sufficiently taxed in 

 supporting the embryos. Yet at this same time, as stated above, small 

 gonads of both kinds of sexual products make their appearance. Al- 

 though such sexual glands are but a small fraction of the size of one of 

 the mature embryos, some of the spermaries often contain a small 

 number of ripe spermatozoa. The ovaries, however, are always very 

 immature, and ajDparently do not mature any of the contained ova until 

 the following season when the worm may again assume the female form. 



The small sj)ermaries, on the other hand, very jsossibly represent 

 the remains of previously well developed glands which have discharged 

 the greater portion of their contents before the maturity of the ova, 

 which at this time have developed into embryos. The fate of such small 

 spermaries is uncertain, for it is improbable that their sjiermatozoa are 

 discharged at a time when ripe eggs are not present in any individuals. 

 It is possible that in some worms they remain until the breeding season 

 and discharge their spermatozoa in advance of the maturity of the ova 

 in the same individual. This would account for the protandric form. 

 In other cases it seems possible that the small spermary might be 

 absorbed by the other tissues of the body, the individual then being 

 looked upon as a female. 



No doubt in many instances the development of the large and 

 numerous embryos weakens the body of the parent to such an extent as 

 to render it susceptible to any unfavorable condition, which may j)er- 

 haps cause death, although there is sufficient evidence to show that the 

 worms often live for two or more seasons. 



The sexual phases are further complicated by the appearance of 

 undifferentiated glands which form both kinds of sexual products. 

 Such glands often occur interspersed among others which form ova only 

 or spermatozoa only. In such an ovo-testis both kinds of genital pro- 

 ducts develop together until the breeding season, when, as a rule, the 

 spermatozoa are discharged before the complete maturity of the single 

 ovum developed in the same gland. 



There is no reason for believing that self fertilization normally 

 takes place in this form, although in a worm which produces both kinds 

 of sexual products such a process may accidentally occur, either from 

 a precocious maturity of ova or from retardation in the development of 

 some of the spermatozoa. 



2 Ztschr. f. wiss. Zool, LIX, 1895. 



