. . entionedmembrane. Two especially interesting groups of muscles, ofunmistakably Annelidan origin, deserve particularattention. These are the rows of dorso-ventralmuscles (Fig. 14, dv.) which pass between the intes-tine and the genital glands in almost exact corre-spondence with the longitudinal muscle dissepimentsso common among the Annelida (cf. Fig. 11, /;;/). Inthe Apodidae, these rows are composed of a kind oflattice work of muscle bundles with definite pointsof attachment, ventrally to the sinewy partitions ofthe ventral musc
. . entionedmembrane. Two especially interesting groups of muscles, ofunmistakably Annelidan origin, deserve particularattention. These are the rows of dorso-ventralmuscles (Fig. 14, dv.) which pass between the intes-tine and the genital glands in almost exact corre-spondence with the longitudinal muscle dissepimentsso common among the Annelida (cf. Fig. 11, /;;/). Inthe Apodidae, these rows are composed of a kind oflattice work of muscle bundles with definite pointsof attachment, ventrally to the sinewy partitions ofthe ventral muscle bands and thus indirectly to thebody wall, and dorsally to the segmental con- SECT. IV THE MUSCULATURE 59 strictions in the integument. In each segment wefind two bands crossing each other diagonally, in ^5 J addition to those placed between the segments. Thesestrikingly Annclidan dorso-ventral muscle bands ofApus are not, as far as we know, preserved in anyof the higher Crustacea, being rendered useless bythe development of the exoskeleton. Clear traces of. ... e FIG. 14.—Transverse section through Apus cancriformis, to show the distribution ofthe musculature. /;, heart; dm, dorsal; VHI, ventral muscle bands ; c»i, circu-lar musculature (as shown in Pig. 15, A), d?>, dorso-ventral musculature ( n, ////); vi, membrane enclosing the intestinal and genital sinus ; /, intes-tine ; g, genital glands ; e, eggs ; a and b have reference to Fig. 15. them are, however, found in Limulus, where theirpoints of attachment have drawn in the outer integu-ment to form the entapophyses. Their use in Apuswill be discussed in the sections on circulationand reproduction. They are not developed in theposterior rudimentary segments. The muscles of the limbs present complications 6o THE APODID^ PART I which might have been expected, when we take intoaccount the transformations which have developedthe latter out of parapodia. It will not be necessaryto describe the muscles of the more
Size: 1786px × 1399px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, bookpublisherlondo, bookyear1892
