170 METAMOEPHOSES OF MAN 



Daphnia.* Nothing of the kind lias been yet observed 

 in the Myriapoda, Arachnida, or Cirrhipedia. 



On the other hand, this phenomenon has been 

 observed in many worms — that is to say, among the 

 inferior annulosa. Apart from the helminthes, whose 

 history deserves to be treated of separately, we find 

 it among the annelids, nemertes, and the naides — 

 small aquatic beings related to the earth-worms. 



Greneagenesis assumes peculiar features in each of 

 the groups which I have enumerated. It was known 

 for a long while under the name fissiparous generation, 

 or fissvparity . In this process, the animal divides 

 itself into two portions. In certain planarias and 

 naides, this division takes place without any apparent 

 preparation, and each isolated portion produces either 

 a head or tail, as the case may be, by gemmation. The 

 animals thus produced are for several generations 

 neutral like the parent ; but eventually, through the 

 operation of conditions of which we are as yet 

 ignorant, the sexes are developed, and the being is 

 propagated by ova. Almost the same thing occurs 

 in a little nemertes which I have often found in 

 the outskirts of Paris; but in it the young being 

 always acquired its head before quitting the parent. 



It is similar with Myrianis and Syllis. In these 

 annelids, the creature which has been thus spon- 

 taneously created, grows from between the final and 



* The origin and development of Daphnia's reproductive bodies 

 have been well described and with considerable detail by Mr. John 

 Lubbock in his excellent " Account of the two methods of repro- 

 duction in Daphnia, and of the structure of the Ephippium" — 

 Philosophical Transactions, 1857. I shall examine his conclusions 

 in another chapter. 



