found in ike Northumberland Lakes. S83 



On placing one of them, PI. VII. fig. 5, under the microscope, 

 the tubercle was found to be vesicular, of a conical form, with the 

 apex obtuse, and to resemble in texture the general surface of 

 the animal: the basal portion contained an opake, rosy, granular 

 body, a, of a glandular appearance, which completely filled the 

 base of the tubercle ; the apex, b, was pellucid, and on being 

 attentively examined a crowd of very minute moving bodies were 

 observed within it. 



Whilst watching with great earnestness the motion of these 

 mysterious bodies, all of a sudden the apex of the tubercle burst, 

 and a great number of them, cloud- like, rushing into the sur- 

 rounding fluid, dispersed in all directions. The rupture appeared 

 to close again, and the apex was seen to be almost empty ; but 

 fresh bodies making their appearance the receptacle was soon as 

 full as ever. I have seen the eruption of these corpuscles on 

 several occasions, and have no doubt that it is a natural phseno- 

 menon ; — not resulting from any artificial means, — certainly 

 not from pressure, as the animals were always quite free. On 

 examining these moving bodies, fig. 12, which are exceedingly 

 minute, with ^th of an inch object-glass, they were found to be of 

 an elliptical form, and to resemble spermatozoa ; tails, however, 

 were not detected, though with a higher power it is not impro- 

 bable that they may be found; for I could not satisfy myself of 

 their non-existence. 



The nature of these tubercles or sacs is a matter of much 

 interest. They were discovered by Ehrenberg, and described 

 by him as the male organ, — the moving bodies being considered 

 spermatozoa. Though I have not seen the original memoir on 

 the subject, I think there can be little doubt of the accuracy of 

 this opinion. How else can we account for the constancy of the 

 appearance of these sacs ? — for their development at the time the 

 eggs are being produced, as we shall afterwards see is the case ? 

 — for their being situated always on the same part of the ani- 

 mal ? — for the contained gland-like body, and moving corpuscles ? 

 — for the eruption of these latter bodies, and for their resem- 

 blance to spermatozoa ? 



Having thus detected what I believed to be the male genera- 

 tive organ, I was anxious to watch the development of the egg, 

 which appears to have been already described more than once ; 

 but as it has rarely been observed by British naturahsts, I will 

 venture to give my own remarks on the subject. The lower 

 portion of the body, as before stated, is enlarged at the time when 

 the male organ makes its appearance. On examining the en- 

 largement, PI. VI. figs. 1 & 2 Z>, 6, carefully, it is found to be 

 usually greater on one side than the other ; here it is opake and 

 of a pale rosy hue, notwithstanding that the animal is faded 



