-o 



iu:production of parts in ckustacka. 47. 



transvei-se section is made, and placed under the microscope, 

 it is found to present the following appearances: — The 

 foramen, for tlie transmission of the vessels and nerves, which 

 was distinctly seen with the naked eye, is obscured on 

 account of the pressure arising from the glass plates, but its 

 situation can be still distinctly made out near to one edge 

 of the section, and also within a thick fibrous-looking band, 

 which, when traced, is found to surround a considerable 

 ext<!nt of surface. The space contained within this band is 

 also found upon examination to be much more transparent 

 than that beyond it, and to contain numerous small cells, all 

 of which have nuclei or nucleoli within them. These cells 

 appear to be suspended in a thickish tran.sparent liquid. The 

 thick fibrous band, mentioned above, is composed of a great 

 many fibres, all of which run almost parallel to one another. 

 Beyond this band, and occupying the remaining space between 

 it and the shell, lies a confused mass of large primitive cells 

 or blastema. The shell membrane, covered by the shell, 

 encircles this, — thus the whole structure of the leg at this 

 part consists of, Isf, the foramen for the transmission of the 

 vessels and nerves ; the fibrous band, with the semi-liquid 

 mass containing small cells ; the blastema of larger nucleated 

 cells ; and, lastly, the shell membrane, covered by the shell. 



In reference to the fibrous band here mentioned, farther 

 observations have proved it to belong to a veiy peculiar 

 system of vessels, which are very generally distributed 

 throughout the body of the animal. They ramify very freely 

 over the membrane lining the carapace, throughout the ovaries, 

 liver, intestinal canal, and on the bloodvessels of the organs 

 of locomotion. In the latter, they are arranged at regular 

 intervals, and run parallel to one another. They run in this 

 manner, until that part of the leg is reached about hiUf an 

 inch beyond the reproductive gland, when they terminate by 

 means of blind extremities. I have not yet made out the 



