METAMORPHOSIS OF CRUSTACEA. 453 



source it obtains the nutriment necessary to its support and 

 growth. Externally the parasite does not present the slightest 

 vestige of any kind of members. 



On laying open the body of the parasite, the external coat 

 appears to be composed of a double membrane, the outer 

 rough, the inner smooth, within which we arrive at another 

 whitish membranous sac, quite loose, except at the neck and 

 lower opening, with both of which it is closely united. This 

 membrane being slit open, a very large and flattened glandular 

 body comes into view, of a white colour and smooth surface, 

 filling the body from side to side, along one of which it 

 is firmly attached to the enveloping loose membrane, as well as 

 to the lower opening, where it terminates by a narrow neck, 

 which is probably its secretory duct; beneath this gland the 

 ample ovary is situated, composed of numerous elongated 

 bunches of concatenated ova, enclosed within a very trans- 

 parent membrane, attached only to the lower opening, where 

 it terminates in two distinct apertures. Hitherto I have not 

 been able to discover any other organs, unless a very small 

 translucent sac, situated at the upper connected edge of the 

 glandular body, and between it and the neck, with which it is 

 also united. Query, — Can this be the stomach of the animal ? 

 Such was the state of my knowledge in regard to this 

 hitherto unobserved and very anomalous parasite, when I 

 accidentally met with one of the above-named crabs in a trawl- 

 boat, having a remarkably large and turgid parasite, from the 

 lower aperture of which issued a purplish granular substance. 

 Subjecting some of this substance to the microscope, it was 

 found to consist of minute larvae (fig. 4), in which it was easy 



