116 



Animal deTelopment often presents us with phenomena of a very curious, 

 exceptional and inexp'ioable nature. I just now mentioned that, as far as is 

 yet known, all British osseous fishes are oviparous with the exception of the 

 viviparous blenny. The medium in which the young of all other species of 

 blennies are developed is the salt water; that in -which this ovo-viviparous 

 species reaches its adult form is at first a peculiar tenacious fluid with which 

 each ovum is supp'ied ; this fluid, as development proceeds, disappears just 

 before the young are born, jirobably by absorption into the body. The ova of 

 other osseous fishes are impregnated after exclusion — it is obvious that im- 

 pregnation in this exceptional case must take place internally ; jet the structure 

 of the generative organs in the viviparous blenny, both male and female, differs 

 in no respect from that of ordinary oviparous genera. It is evident therefore 

 that the fertilising fluid of the male must find its way to the ovaries of the 

 female. How are we to account for this curious exception to the general rule. 



The development of the young of the Syngnathid» or pipefishes is very 

 curious, and presents phenomena which call to mind the IManimiferous 

 Marsupials, with, however, this marked difference, that in the Mammiferous 

 Marsupial it is the female that has the pouch, in the fish the male. This pouch 

 consists of two large valves beneath the tail, posterior to the cloacal orifice ; 

 internally the surface is indented with a number of cells ; in these cells the eggs 

 are hatched and the young pipe-fishes developed ; and Blr. Couch tells us that 

 even after they are fully formed a kind of attachment still continues between 

 the parent and the young, for in case of alarm, th(y fly again to the shelter of 

 the pouch and are readily received into it. I should mention that the female 

 pipe-fish herself deposits her eggs into the marsupium of the male who opens it 

 to receive them. A still more curious mode of piscine embryological develop- 

 ment has recently been investigated by Agassiz as occurring in certain species of 

 fish he found in the basin of the Amazons. The locality, in which the ova 

 are developed, is certainly one which you never could have guessed ; it is 

 absolutely in the mouth ! In a letter to Milne Edwards dated September 22nd, 

 1865, Professor Louis Agassiz thus writes of a species of Oeophagus : " This fish 

 has a most extraordinary mode of reproduction. The eggs pass, I know not 

 how, into the mouth, the bottom of which is lined by them, between the inner 

 appendages of the branchial arches, and especially into a pouch formed by the 

 upper phar3mgeal3 which they completely fill. There they are hatched, and the 

 little ones, freed from the egg-case, are developed until they are in a condition 

 to provide for their own existence. I do not yet know how long this continues, 

 but I have already met with specimens whose young had no longer any vitelline 

 sac, but were still harboured by the progenitor." 



At page 238 of "A Journey in Brazil," further information is given of 

 these fish. "The story of ihe A ca ran, the fish which carries its young in its 

 month grows daily more wonderftd. This morning Mr. Agassiz was off before 

 dawn on a fishing excvirsion with Major Eatolano, and returned with numeroua 



