Boyal Microscopical Society. 63 



bands of Ascaris, seems to me to be indicated in tbe want of 

 muscularity in the intestinal canal of Ascaris : and its remarkably- 

 modified form in Mermis, where it is entirely deficient, except in 

 the anterior part of the body. Again, it is difiicult to doubt the 

 affinity between the Nemertida and the Nematoida. 



I have little to say further on the anatomy of Ascaris, the 

 reproductive organs have been so carefully described by Cloquet, 

 Dr. Cobbold, and others. I will only add to their descriptions that 

 the walls of the ovaries uteri and vagina, as well as of the testis and 

 its duct, have a distinct muscular coat, upon which nerves and 

 pseudo-haemal vessels may be traced. 



I have also a few facts to add concerning the development of the 

 sexual elements. 



The ova in the upper part of the ovaries somewhat resemble 

 conical epithelial ceUs, and fill the whole ovarian tube, meeting 

 in its centre or axis. They are white and very granular, and 

 exhibit no distinct cell wall. I am doubtful about the nucleus, 

 but believe I have detected it in several instances. These conical 

 ova are more loosely packed in the lower six or eight inches of the 

 ovarian tube, and begin to -exhibit traces of division at their base. 

 Lower still they have formed distinct buds, which become detached 

 and form the yelks of the eggs. Meisner has observed a similar 

 process of multiplication of ova in Gordius, and in some Lamelli- 

 branchiata. In the larger part of the genital tract, the so-called 

 uteri, the ova become invested first in a strong yelk-capsule, and 

 later in a beautiful sculptured chorion. The ova are deposited in 

 strings, hke those of Blermis, adhering by the chorions. 



It has been stated that several months elapse, during which 

 period the ova need to be submerged in water, before development 

 proceeds in them to yelk segmentation; but I have specimens of 

 eggs taken from a worm, which was placed in spirit as soon as it 

 was voided, which exhibit several distinct stages of yelk segmenta- 

 tion. 



The male sexual element exists in the upper part of the tubular 

 testis in the form of minute distinctly nucleated caudate cells, 

 attached to each other in a manner precisely similar to the budding 

 ovarian cells ; they do not exceed the i^^oWth of an inch in their 

 long diameter. Lower down in the testis they are polygonal from 

 pressure, and have increased to ysVoth of an inch in diameter, still 

 with conspicuously bright nuclei. The nuclei are replaced in a more 

 advanced part of the testis by bright nuclear particles, of which 

 there are from twenty to thirty in each cell. The remainder of 

 the male sexual canal, which is very capacious in proportion to the 

 testis, was entirely filled with similar cells, so that I am ignorant 

 of any further changes which they may undergo. 



The development of the ova as far as it is at present known has 



