442 Prof. A. Schneider on the Develojjment 



The embryo, or, rather, the hirva proceeding from it, divides 

 very soon into two haycrs, a thick dermal Layer and an inner 

 cell-mass, from whicli the other organs originate. The dermal 

 layer is characterized by very large spherical nuclei with 

 nuclear corpuscles : these at first lie irregularly scattered, but 

 they then aiTange themselves in the following manner : — At 

 the cephalic extremity a band of six nuclei is formed, between 

 •which the six foremost hooks protrude. A second band, of 

 about fourteen nuclei, is formed at the place where the lemnisci 

 are produced. The nuclei of this band become the nuclei of 

 the lemnisci : while the latter grow inwards as two processes 

 of the skin, the nuclei graduallj'- pass into them. Of the 

 remaining nuclei the hindmost four, with their nuclear cor- 

 puscles, increase considerably in length, and accompany the 

 lateral lines of the body on each side as four cords. In the 

 mature state they attain nearly the whole length of the body, 

 and are probably the longest nuclei known. 



Between the lemniscal band and the anterior extremities of 

 these four nuclei, a considerable number of nuclei are rather 

 irregularly placed ; these also increase in length, but in a 

 much less degree. All these long nuclei, as also their nuclear 

 corpuscles, give off short acute diverticula on both sides. 

 These large, long nuclei are still found in the mature exam- 



f)les. Without the history of the development, their morpho- 

 ogical signification could hardly be guessed. 



Both the ovaries and the testes are produced extraordinarily 

 early. The former are two bodies, each composed of about 

 four cells, and are both situated at tlic same place. Each 

 testis is connected by a cord, consisting of a series of cells 

 (afterwards the efferent duct), with the well-known muscular 

 vas deferens. The ovaries are from the first destitute of this 

 or any similar connexion. "While the testes grow rapidly by 

 cell-multi})lication, the ovaries remain unaltered, and probably 

 fall away from the so-called ligament very early (when the 

 total length of the animal is 5 millims.). I have been unable 

 to ascertain the subsequent fate of the ovaries. 



The nature of the so-called " liga- 

 mentum suspensorium " has hitherto been 

 entirely mistaken. In the transverse sec- 

 tion of the mature female, and indeed 

 almost throughout the whole length from 

 the anterior end of the uterine bell to the 

 insertion of the retractores proboscidis, 

 the ligament shows in the manner re- 

 presented in the figure. It consists of 

 fine membranes which, as may be seen, bound two sacs (a 



