382 Bibliographical Notices. 



licle- cells are supposed to originate. Towards the side of the sup- 

 porting membrane the germinal cells diminish in extent and pass 

 insensibly into the common epithelium of the body-cavity. 



At the young top of the ovary no evaginations occur ; only a fold 

 of the body-wall shows the direction in which the genital gland is 

 growing. On this fold some of the ccelomic epithelium-cells have 

 increased in size, especially with regard to their nucleus, and show 

 the features of young egg-cells. 



By these results the author is led to the conclusion that the ger- 

 minal epithelium is a specially differentiated part of the epithelial 

 layer of the body-cavity. 



In the nephridial canals that open with funnel-shaped mouths 

 into the body-cavity egg-cells were often found, this fact proving 

 that, when necessary, the reproductive cells are evacuated in that 

 way, and not, as Gratiolet believed, by pores in the mantle-tissues. 

 The impregnation is supposed by the author to take place in the 

 sea-water, into which both eggs and spermatozoids are evacuated 

 through the genital funnels ; because he cannot believe spermato- 

 zoids to enter the body-cavity of females by the small external 

 openings of these ducts. 



The brown spots on the surface of the ovaries, supposed by Han- 

 cock to be the places of origin of the sperma, were found to be accu- 

 mulations of egg-cells undergoing retrogressive metamorphosis. They 

 were also found on the testes, and there consisted of spermatozoid 

 mother cells undergoing the same degeneration. 



The microscopical structure of the muscles was found to be as Han- 

 cock describes it. They consist of thin longitudinal fibres, perfectly 

 parallel, and probably as long as the whole muscle itself. Apposed 

 externally to these fibres were found nuclei surrounded by a minimal 

 quantity of protoplasm. From this fact, the author believes in 

 the epithelial character of the muscles, which probably have origi- 

 nated from the ccelomic epithelium, and, in becoming independent 

 of it, have retained the nuclei of their formative cells. 



All muscular fibres were found to be smooth, with the exception 

 of those of the posterior occlusors, which are distinctly striated. In 

 this fact, already mentioned by Hancock, the author sees a new 

 proof for the assertion of the Hertwigs, that between smooth and 

 striated muscles there need not be any morjjhologieal, but only a 

 physiological difference. The occlusores posteriores and anteriores 

 have the same function ; they are inserted on the same tendinous 

 mass ; but the former are striated, the latter smooth. 



The results the author believes he has obtained are summed 

 up by him as follows : 



1. The free parts of the body- wall are covered everywhere with 

 a monocellular epiblastic epithelium. 



2. Beneath this epithelium is found a mesenchymatie layer of 

 homogeneous substance with interspersed multipolar cellular 

 elements. 



3. The tendinous parts of the muscles and the whole peduncle 

 are highly developed parts of this mesenchymatie layer. 



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