52 SUMMARY OF CURRENT RESEARCHES RELATING TO 



From the extremity of its suckiug tubes as far as the superficial 

 boundary of the body the Sacculina is traversed by a system of lacuna© 

 in which there circulate the liquids taken in by the tubes and which 

 forms a rudimentary digestive and incubatory apparatus. 



Some of the spaces between the muscles of the visceral mass are 

 occupied by sinuous tubes which are filled with ova, and are invested 

 by the general endothelial layer. The ovaries open into the incubatory 

 pouch, not far from the cloaca. There are two testicles, one on each 

 side of the middle line, which open into the bottom of the pouch. 



The nervous system is formed by a single ganglion which is 

 situated in the visceral mass, near the cloacal end ; this end, therefore, 

 is the cephalic or upper one, and not the lower, as has been ordinarily 

 supposed. This ganglion has the form of a four-rayed star, whence 

 four chief nerves are given off; the two upper ramify in the muscular 

 layer, giving off an important branch to the cloacal sphincter. The 

 two lower pass to the visceral mass, some dividing into two branches, 

 one of which innervates the muscular layer of the envelope, and the 

 other the transverse muscular layers. 



Two or three days after a Sacculina has set free its NaupUus it 

 gives off some more ova; the chitinous layer which clothes the in- 

 cubatory pouch undergoes ecdysis and passes out by the cloacal orifice. 

 A new layer is formed, a number of ramified chitinous tubes escape 

 from the oviduct, to the base of which they remain attached. The ova 

 are now driven into and fi.ll these tubes, which later on become 

 detached and remain in the incubatory pouch till the ova are matured. 

 The eggs are fertilized in the ovary. 



In a second note on Sacculina* M. Delage has some observations on 

 an internal stage in its development ; he finds that an early period is 

 passed by the parasite within and not without the body of the crab ; 

 it is there found in a completely developed state, having its generative 

 organs and its nervous system completely developed ; and it is only 

 when it grows larger that it changes its position. At the moment 

 when it does so the orifice of its cloaca is closed and completely sur- 

 mounted by a delicate chitinous membrane ; a little later this breaks, 

 and young Cyprids make their way to the periphery of the cloaca, 

 where they become attached. All young Sacculinse have Cyprids fixed 

 to their cloaca, and these, therefore, as Fritz Miiller supposed, play the 

 part of complemental males. 



In a third note| M. Delage considers the development of the 

 Cypris; he finds that the young leave the incubatory pouch of the 

 Sacculina under the NaupUus form. During the five ecdyses that take 

 place in the next four days the two pairs of biramose appendages are 

 lost, and the Cypris with its six pairs of limbs, its fixing organ, 

 antennee, and internal spherical mass of small cells, becomes developed. 

 For three days or more the Cypris swims about freely ; it then, either 

 during the night or at some dark spot, attaches itself to young and 

 very small crabs ; this fixation is always effected by one of its 

 antenna), is always on a hair of the body, and is never on the ventral 



* Tom. cit., pp. 1012-4. 

 t Tom. cit., pp. 1145-8. 



