Reproduction of the Chitons. 447 



low, and of subglobular form, being a little compressed or 

 oblate at what may be termed the axes ; each appeared about 

 100th of an inch in diameter. I may here remark that the 

 animal now mentioned was the only one that deposited ova. 



The animal, previous to the exclusion of the ova^ had moved 

 from the flat position it occupied on the stone to its edge, and 

 elevating by reflexion the posterior portion of the coriaceous 

 skin in which the valves are imbedded, poured out for several 

 minutes a continuous stream of flaky white matter like a fleecy 

 cloud, which proved of a glutinoiis nature, and probably pro- 

 ceeded from the organs which M. Cuvier and authors have con- 

 jectured to be a pair of symmetrical oviducts, but which they 

 failed to trace to an external outlet : I rather think that they 

 are glands, and that their use is to provide the material for the 

 capsule or membranous envelope that contains the mass of each 

 ovum, and also to entangle by its tenacity the congeries of ova 

 which followed its emission to prevent them being washed away 

 by the water, as when I attempted to remove one or two, I 

 found they were slightly retained by adhesion : it is probable 

 that the cloudy vapour when condensed into fluid serves for a 

 nidus until the young are prepared to emerge from their cells. 

 I did not succeed in ascertaining if the viscosity issued from an 

 organ, or pair of organs, or glands distinct from the oviduct : I 

 can only say that the ova as well as the thin smoke-coloured 

 matter were excluded from under the centre of the coriaceous 

 integument of the posterior terminal valve, in a similar manner 

 as I have described them to be discharged from the posterior 

 extremity of Dentalium, 



I carefully inspected the ova throughout the 24th July ; they 

 remained inert at the bottom of the saucer ; but on the morning 

 of the 25th I was greatly surprised to find that all had become 

 detached from their nidus, or position, and swam with great 

 vivacity through every part of the water, sometimes at the sur- 

 face, sometimes in the middle, and at others at the bottom ; 

 these minute objects moved with extraordinary speed, crossing 

 a large breakfast-saucer in 30 or 40 seconds. 



As soon as motion had commenced, the ova lost the sub- 

 globular figure, and assumed that of a subelongated oval ap- 

 proaching the Chiton shape. It has already been stated that 

 each ovum was imbedded in a pale yellow membrane, but when 

 the rapid swimming action took place, only half of the animal 

 was liberated from the capsule, the anterior skin being reflexed 

 or withdrawn on the still adhering posterior portion, forming a 

 ridge that divided the animal into two sections. With a power 

 of 300 linear I could see the elements of the four anterior 

 valves, as well as the buccal depression and head : this very early 



