HACDOKALD ON HETEBOCTATHX7S jLND 8IPUKCX7LX78.
81
the body was lined with a ciliated membrane, which was reflected round the larger branches of a transparent (probably water) vascular sys- tem running along the spirally coiled intestine, with its singularly constructed central suspensory ligament. All this militates against the supposed Echinoderm nature of Sipunculw, and give it radiating aflSnities with the Annelida^ Folyzoa and Tunicata, though perhaps only of a representative kind. The simple anatomy of the larval form, the^^^M of Peron, if it be not indeed a permanent one, is also of great importance in this connexion.
Bbfbrxkces.
1. Sipuneulus ffeteroeyathi, (nataral size) a. Opercular disk. h» candal disk.
2. Ventral view enlarged, a. Opercular disk, b, caudal disk, e, proboscis. 8. Dorsal view enlarged, a. Opercular disk, b, anus, e, proboscia.
4. Coiallnm« seen frran above, enlarged, a. Columella, b. primary. 0. secondarj and d, tertiaiy ravs. $, primary. /. secondary and g, tertiary loculi. hJi.h. Open- ings communicating wiUi the burrow.
5. Lateral view, shewing a. the aperture of the burrow.
[The case of parasitism here described has an especial interest if viewed in relation to the apparently anomalous characters of the palsBozoic Pl^iiyWitf/^^ft, which wfr aie much incUned to regard as a oocal perforated in a simiUr maimer. — Sxw.] N. H. R.— 1868. G
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