68 REPORT — 1844. 



consists apparently of one, the absorbing membrane onlj', further back the external 

 membrane becomes visible, and as portions are examined under the microscope, it is 

 found to become thicker and thicker as it nears the posterior part of the cyst. The 

 remains of this cyst can be traced for many feet in length in the tissues of the in- 

 fested being, in the form of a delicate cord. 



On the Reproduction of Lost Parts in the Crustacea. 

 By Harry D. S. Goodsir, M.W.S. 



That all the species of Crustacea are endowed with the power of regenerating parts 

 of their body which have been accidentally lost, is a fact which has been long known. 

 The manner, however, in which these are developed, and the organ also from which 

 the germ of the future leg is derived, has never yet been either properly explained or 

 examined. If one or more of the distal phalanges of the leg of a common crab be 

 torn forcibly off, the animal instantly throws off the remaining parts of the limb. 

 This is effected with little apparent exertion, and always takes place at one spot, which 

 is marked externally by a delicate line covered with an annulus of thinly-scattered 

 hairs. The phalanx on either side of this ring is considerably contracted, and when 

 the shell is taken carefully off so as to expose the interior, it is found to consist of a 

 fibrous, gelatinous, glandular-looking mass — the organ which supplies the germs for 

 future limbs. 



The microscopic structure of this organ is extremely beautiful. When a thin trans- 

 verse section is made and placed under the microscope, it is found to present the fol- 

 lowing appearance : — 1st, a foramen near to one edge for the transmission of the ves- 

 sels and nerves ; then a semiliquid mass containing small nucleated cells, which is 

 surrounded by a fibrous-looking band ; beyond this band lies a mass of blastema of 

 large nucleated cells ; and lastly, the shell membrane covered by the shell incloses the 

 whole. 



The fibrous-looking band here mentioned is found from further observations to 

 belong to a very peculiar system of vessels very generally distributed throughout the 

 body, and which all terminate by means of shut sacs, on each of which a dark cir- 

 cular spot is observed, having all the appearance of a germinal disc. The author, 

 from want of time, has not been yet able to make out the relations of these vessels. 



Some hours after the limb is thrown off, the small foramen becomes gradually 

 filled by a small rounded body (the germ of the future leg), which gradually increases 

 in size so as to push out before it the cicatrix which had been formed on the raw sur- 

 face after the injury, and now forms the external covering of the young limb. As the 

 germ increases in size, the inclosing membranes become thinner and thinner until 

 they burst, when the young limb, which has hitherto been bent upon itself, becomes 

 extended, and has all the appearance of a perfect limb except in size. As far as the 

 observations of the author had gone, it appeared that the germ was derived from one 

 of the cells nearest the foramen. This cell follows the ordinary course of develop- 

 ment, by the nucleus breaking up into nucleoli which in time become parent cells 

 also, each of which undergoes the same process. This goes on for several stages, all 

 the less important cells dissolving and serving as nourishment to the central or more 

 important ones, until the number of centres are reduced to five — the number of joints 

 required, which, by a regular process of a similar nature, assume the form of the 

 future leg. 



On the Morphology of the Reproductive System of Sertularian Zoophytes, and 

 its Analogy with that of Flowering Plants. By Prof. E. Forbes. 



At certain periods in the life of the sertularian zoophytes, which are composite 

 beings of plant-like forms, constituted of numerous nutritive individuals which, be- 

 sides the life of each share in the common life of the whole, there appear on the 

 axis or branches variously formed bodies, in some species urn-shaped, in others pod- 

 shaped, very dissimilar from the other parts of the whole, in which, after a time, the 

 ova are formed. These are the ovigerous vesicles of naturalists, the true nature of 

 which has been often discussed, but hitherto unexplained. These bodies. Prof. E. 

 Forbes maintains, are branches of many individuals which have undergone an ideal 



