78 



Their protoplasm has. iisuallw a pi-omincnt s^'lolnilous stnirture (PI. \'III, fig. 12) whicli is I'spcri.illy ohsrrwiliK- 111 M. s^rafti, 

 M. giganteiim, M. carpcntcri etc. I think, that these globules must lie absorbed nutritive sulistance. Cells of M. rirri- 

 ferum are, in fresh state, blackened by osmic arid, which would appear to show that they contain fat. In M. cirriferum, the epi- 

 thelium is higher on the dorsal side of the branches than on the ventral side. A similar tendency can, usually, be traced in the other 

 species; the cells, however, vary, in a great degree, in length, .is well as in fnrm .iiid appearance, vide Pi. Mil, lig. 12 and 13. 

 I think that this variation is, partly, occasioned by the cells being, mon- or less, filled with nutritive substance. ( Jn the outer 

 side of the membrane surrounding the intestinal branches, muscular fibres are, frequentl_\'. ol)served, one end of which is se- 

 cured to the membrane. In these membranes, trans-sected canals are also observed (fig. 12. a.\ 



The rectum is divided from the stomach b_\- an annular protuber.ance in tlu' epithelium, caused b\- the epithelial 

 cells in the posterior part of the stomach being very long and prominent, whereas, in the anterior part of the rectum, the 

 cells are very much flattened, especially on the dorsal side; just in rear of the before mentioned protuberance, two oviducts 

 open into the rectum which, therefore, becomes transformed into a cloacal canal (figs. 20 and 21). At the posterior extremit}-, 

 close to the anal aperture, a third dorsal oviduct opens. The epithelium is, to a certain extent, ciliated, especially in the 

 posterior end. In the posterior portion of the cloacal canal, in most species, the epithelium forms longitudinal ridges. The 

 cloacal canal is surrounded by a muscular layer, considerably less developed and continuous, however, than that of the stomach. 



Glandulous tissue surrounding the alimentanj canal. I have observed, in M. graffi especially, a peculiar tissue sur- 

 rounding the posterior part of the stomach, on the dorsal, as well as on the \'entral, side (PI. II, fig. 3, m. v. k.) and which is 

 extended over the anterior part of the rectum. This tissue has a remarkable structure which is seen illustrated in PI. \TI. 

 fig. 23. Numerous large nuclei are visible, Lnit, at same time, a great inan\' minute corpuscles, or nuclei, can be observed 

 destributed throughout the entire tissue. I l:)elieve the function of the tissue must be secretive, but I have, however, not 

 detected any secretory opening into tht- stomach or rectum. In the other species examined, a similar tissue is but little 

 developed. In the connective-tissue surrountling the stomach, nerve-cells are, frequently, observed; these, I think, belong to a 

 s^-mpathetic ner\-ous system which I ha\e, however, not submitted to exemination. 



Genital organs. 



Female genital organs. The ova are, I think, derived from the epithelium of the bod>--cavity ; remnants of this 

 epithelium are only found, now, in the mesial dorsal portion of the bod}'-cavity, the uterus and approximate parts; the epi- 

 thelium occurring here is ciliated, and flattened (PI. VII, fig. 2j). On the dorsal side of the stomach, one or two pairs of 

 organs occur (PI. II, fig. 6 and 15, ov.r., PI. L\. fig. 23 ovr.); these organs are situated in, more or less open, branches 

 issuing from the uterus, and consist of crowds of small cells with dark staining nuclei and nucleoli (PI. \TII, fig. 2},). I have 

 found ova close to these organs, vide fig. 23 ov. I consider these organs to be traces of the primordial ovaries which have, 

 however, degenerated, tin- e])ithelium of the body-cavity acquiring the function of producing ova. There are three o\iducts. 

 One dorsal oviduct, w'hich has been described by Graft", has a very minute aperture which, in sections, is very difficult to 

 distinguish. I am not certain whether in some species, e. g. M. giganteum, the aperture is not separated from, and situated 

 at the side of the cloacal aperture. Besides this dorsal oviduct, there are two lateral, or \'entral, o\'iducts issuing from the uterus 

 and passing down, one on each side of the stomach, towards the ventral side, vide PI. I, fig. 1 1 ovd. here, thew pass back- 

 wards, and open into the anterior end of the cloacal canal, vide PI. I, fig. 8, PI. IX, fig. 10 and 23. The epithelium of these 

 oviducts is much ciliated (PI. VII, fig. 26); it is of a secretorj' nature, and mucous globular secretions of variable size are often 

 observed in it, vide PI. VII, fig. 25, a. Besides being oviducts, these ducts ma}-, probably, be regarded as respiratory ducts. 

 The cilia at the openings into the cloacal canal are, usuall}', found to be directetl inwards into the ducts. From the descrip- 

 tions of Graft" and previous writers, we know that seawater passes through the anal opening into the cloacal canal; m,iy it not 

 pass thence into the oviducts (:}). On the assumption that the function is respiratory, the meandering course may also be ex- 

 plained Knit if the function is, onl}- that of oviducts, the latter is difficult to account for. The o\-a, usuall}-. have a globular form. 

 In the nucleus, I have, frequently, observed small globular bodies; whether they are .■malogous to those of Amphibia and 

 Insects described by Will'), as Beard supposes, I have had no opportunit)- of examining. 



Male genital organs. The testes arc, principall)', situated between the alimentarj- canal and the nervous system, but 

 man)- of their branches are, however, situated between the lateral branches of the alimentar_\- canal. I h;u-e observed in one 

 species, M. cirriferum, several Ijranches of the testes extended to the ectoderm of the dorsal sitle aiul the margin of the 

 body, vide PI. II, fig. 5 t. I have observed, in other species, small isolated testes under the ectoderm in the margin of the 



>) Zool. Anz. 1884, No. 167, 16S. 



