THE TREMATODA. 101 



breeding which takes place between the skin and the 

 viscera, and the inchision and incipient development of 

 the ova in the so-called " loose ovaries^' during the con- 

 tinued growth of the latter. I must confess, that I look 

 upon these oval bodies much rather as individuals which 

 will never quit the parent animal, than as " ovaries;'' and 

 till their true nature is known I shall regard them as 

 such, and consequently consider most of the JEchinorJiyncJd 

 hitherto known, as "nurses'' It is confessedly uncertain 

 whether the EcJdnorhpicJd spend part of their life exter- 

 nally to the organism which they inhabit as full-grown 

 animals, or not ; it is however very probable they do so, 

 as the embryo attains no real development in the ova 

 so long as these are in the Eclimorhynclms ; and the ova 

 are met with in the mucus of the stomach and in the 

 excrements, by thousands, in the same condition, so that 

 the development of the young in the ova and their escape 

 from them, certainly occurs very long after the ova have 

 reached the water.* 



With this I connect the remark, that in the months of 

 February, March, and April, I have often found in the 

 mesentery and cellular tissue about the liver and intes- 

 tine of the sole, very minute individuals of from \ '" — § '" 

 or sometimes even 1 '" in length, all of which were inclosed 

 in a thick membranous cyst, of a more or less regular 

 oval form. When these cysts were opened (fig. a, tab. iii) 

 there came out of them a very much contracted JEchino- 

 rhynchus (fig. h) whose organ of attachment, fm-nished 



* A remarkable exception must be made, however, in the case of a species 

 of Echinorhynchus examined by Professor Eschricht, and in wliich he observed 

 innumerable ova, in which the embryo was so much developed, that at first 

 the egg membrane escaped his notice, and he believed the embryos had been 

 hatched. As this observation was made on an Echinorhpichus of the common 

 haddock of Copenhagen, and as the Ecliinorkynchi of this fish, as well as of the 

 sole, which appear to be the same species, have been examined by many, it 

 is the more remarkable that this condition was not earher noticed ; I have 

 myself, during several months, examiaed the Echinorhynchi of our common 

 sole, but there has been no trace of an embryo ui their ova, although tlie 

 latter were passed by thousands in the excrement. [May it not tlien probably 

 have been an ascaris or some other nematode which Professor Escluicht had 

 before him ?] 



