On the Life-History and Development of the Genus Myzostoma. 57 7 



If tlie genus Myzostoma was once imisexual, what has brought 

 aboiit the change to Hermapliroditism? The auswer is probably the 

 tbllowing. The necessity of it for the continued existence of some spe- 

 cies of the genus. The eggs are veiy small , and hatch a minute free 

 swimming larva, which has to trust very much to chance to find a 

 future host. Only by the development of a vast number of eggs , and 

 the provision of efficient means for the fertilisation of those eggs is the 

 continued existence of some species of the genus rendered a possibility. 



The first condition, the development of a vast number of eggs, is 

 realized to au astonishing degree. One has only to examine a full grown 

 specimen of Jf. glahrum or M. cirriferum to assure himself of this. I 

 have often been astonished at the enormous number of eggs contained 

 in one M. cßabrum. When v^e consider too that this production of eggs 

 is a continous one extending over at least some months , and that eggs 

 are probably laid daily , it is evident that each individuai in its lifetime 

 produces vast numbers of eggs. But the production of eggs is not the 

 only factor. — They must be fertilised. The difficulty of the continued 

 existence of the species is increased by this fact. For if the chances of 

 one larva finding a host are exceedingly small, the chances of two 

 larvae , which when adult will be male and female respectively, Coming 

 to occupy the same host must be much smaller. And in many cases 

 only two or more females would get to one host. This latter state of 

 thiugs would become much more intensified if for any reason the num- 

 ber of males produced from the young larvae should in some way or 

 other become diminished. Hence it becomes of advantage to comple- 

 ment the small males by the development in the female of testes , from 

 part of the female organs as in Amphibia. It may well be that at first 

 the testes only become functional in particular cases in which females 

 alone without males occupied a particular Comatula. In time the pro- 

 gress to complete hermaphroditism becomes more and more pronounced, 

 and finally in some cases the males become lost. 



This extinction ^ of the males may be brought about by a diminution 

 in their size and a corresponding increase in size and number of herma- 

 phrodites, which devote themselves to the production of eggs and sper- 



1 This extinction of the males might be brought about by a periodicity in 

 their occurrence arising. If the periodicity got more and more lengthened, it 

 would in the end become so to speak infinite , and the males would disappear. 

 Compare Weismann, Über die Entstehung der cyclischen Fortpflanzu%g bei den 

 Daphnoiden. Abdruck aus d. Zeitschr. für wiss. Zoologie, 27.-33. Bd Tiere such 

 a periodicity is associated with a somewhat different result, viz. Par ■ jgenesis. 



Jlittheilungen a. d. Zoolog. Station zu Neapel. Bd. V. 38 



