76 



The body-cavity and the connective-tissue. 



A delinite bodj'-cavity is, in my opinion, not present; wliat ma}' be considered as rudiments of it, are the cavities 

 in which tlie ova are situated. These cavities may be quite filled with ova, but sometimes they are nearly empty and ha\e 

 ova situated in an interrupted layer along the walls. The ovaries are derived from the epithelium of the bod}--cavity, and 

 this epithelium is, now, onl\- remnant in .^ome particular places, especialh- in the --uteruss and adjacent parts on the dorsal 

 side, where it can be seen as a thin ciliated epithelium, \ide PI. VII, fig. 27. 



The body-parenchyme consists of a reticular connective-tissue. The size of the meshes, in this tissue, varies in 

 the difterent p.irts of the body. The nuclei are oblong and have a granular appearance, the granules appearing as thickenings in 

 the chromatic structure, vide PI. IX, tig. i;. The nuclei are, usualh-, situated in the fibres forming the meshes, and consequent!)', 

 not in the meshes themselves, as described b\- Gratt". I have onl)- obsen-ed such a nucleal situation in some special parts 

 ol the body, particularly in the connective-tissue of the anterior proboscis (Pi. IV, fig. 6 and 7), 1 have not observed 

 »Rundzellen which, according to his description, is identica] with iden durch die Leibesfliissigheit frei im Korper umher- 

 getriebenen : Blutzellens:,': and from which, also, the ova are supposed to be derived, nor have I met with connective-tissue 

 nuclei of the globular form described bv hmi. 



Muscular system. 



PI. MIL fig. 26 illustrates some dissociated dorso-ventral muscular fibres. The nuclei are, usually, situated in pro- 

 toplasmic prominences at the side of each fibre. The extremities of the muscular fibres are divided into several branches, 

 between which protoplasmic remnants, are seen (probably of connective tissue). Sometimes the nucleus is situated more 

 towards one of the extremities (bj; I have even seen it situated between the branches (a). 



Segmental glandulous sacks ( Suckers ). 



What previous writers have called .suckers» are not, really, such, but ciliated glandulous sacks, as illustrated in 

 PI. \TII, fig. 19 and 20. There are no muscular walls such as Graft' has described. The inner walls consist of a glandulous 

 tissue, with large cells situated in one, or several layers; this tissue is covered bj- a ciliated cuticle, which is striated by the 

 cilia penetrating it into the tissue, vide figs. 19 and 20. Only a few muscular fibres occur in the walls of the sacks, and those 

 are, usually, dorso-ventral muscles which penetrate through the glandulous thissue and are secured to the cuticle by their ex- 

 tremities, vide fig. 20, m. In M. glabrum, the glandulous tissue is separated from the surrounding connective-tissue b}- a 

 cuticle, on whose exterior side several muscles are situated, and I have not observed such a clearl\" defined cuticle in the other 

 species examined. In the surrounding connective-tissue, vacuoli frequenth- occur. Among the glandulous cells, connective-tissue 

 nuclei can be seen; this is especiall}- the case in M. graffi, and M. giganteum. — The openings of these sacks are, more or 

 less, prominent in the various species, and the thickness, of their oral margins, also varies very much, vide PI. Mil, fig. ig and 20. 

 The form of the opening is. in some species, circular (e. g. M. cirriferum fig. 22) and in others, oval (e. g. M. giganteum fig. 21). 

 The openings are provided with sphincters, which var}- in development in the wirious species; in some species the}- are few 

 in number, and thick (e. g. M. cirriferum, fig. 20, sph.) whilst, in other species they are more numerous, but are, then, less 

 developed in thickness (e. g. M. giganteum, fig. iq). Round the openings radial fibres, also, occur, whose function is to act 

 as dilatatores, vide fig. 18, m, m'; fig. 21 and 22. 



What is the ph}-logenetic development of these organs.' Are the}- homologous with the segmental organs, 

 or with the dermal glands of the Geph}-reans for instance, or perhaps, with the trachea of the Arthropods.'' In the present 

 state of our knowledge we are unable to determine this question. The greatest disagreement, between the organs w-e have 

 described and the segmental organs of the Annelids, consists in the fact that in Myzostomida the}- do not communicate with 

 the body-cavity. This cirrumstance may, however, be explained b}- the degeneration, or partial disappearance, of the bod}--cavit}', 

 during which process the segmental organs have become transformed into these w-e find in the present Myzostomidae. Whether 

 these glands are related to the >,segmental organs- described b}- Huet ') as existing in the greatest part of the terrestrial 

 Isopods, is not eas}- to determine. They agree in not ha\-ing an}- open communication w-ith the body-cavit}-, but in their 

 structure, otherw-ise, they seem to be quite difterent. 



•) Huet: Sur I'existeiice d'orgaues segmentaires chez certain Crustacés isopodes. Comptes Remlus 1882. T. i. p. 810 — Sir. Regarding 

 these glands he states; «lis manquent a la tete. Ils s'ouvrent a la jiartie supérieur des epim^res de chaque cote par une ouverture en crible. Cela fait 



done pour les septs anneaux du corps, quatorze glandes < «Certains des elements cellulaires mesure nn cinquitime de millimetre .... Entre eux 



s'etend une sorte de vestibule d'ou part un conduit rempli par la mati^re.sécrétée. < .\ccording to that description, it would appear tliat these glands have 

 more resemblance to the parapodial ganglia of M. graffi. 



