44 MES. LEONORA J. WiLSMOllT?. ON SOME 



of the si})honoglyphe, remain the largest. The pairs 4 4, 5 5, and 6 6 

 have lost their digestive endoderm entirely and are of about equal size. 



The incomplete mesenteries (PI. 4. fig. 3, imper.mes.) have longitudinal 

 retractor muscles on plaitings the same width throughout ; their parietal 

 muscle does not form tufts, and they are not provided with digestive endo- 

 derm or mesenterial filaments. At the posterior end of the scapus they are 

 already very minute (PI. 4. fig. 7, imper.mes.). 



In the larval form there are present twelve tentacles and twelve fully- 

 developed perfect mesenteries, two pairs of which, viz., 5 5 and 6 6, are 

 unattached to the oesophagus. All twelve have muscle-pads, digestive 

 endoderm, and mesenterial filaments. No mesenteries of the second cycle 

 are present. 



Pliysa. — In this region there are a number of pores through the body- 

 wall. There is no external evidence of their presence, and some of the 

 sections being broken, I am unable to give their total number, but have 

 counted over sixty. The physa was cut longitudinally, and I cannot deter- 

 mine whether, as in some species of Halcarnpa, there is a central pore, round 

 which the others are arranged. These pores are placed in longitudinal rows, 

 and are much more numerous in the lower half of the physa than in the 

 upper. Two or three occur on adjacent parts of the scapus. PI. 4. fig. 6 

 (1, 2, 8, 4, 5) shows a longitudinal section of the physa-wall with five of these 

 pores cut through in different parts of their course. The mesogloea between 

 the small suckers of the physa is extremely thin and covered with a thin 

 layer of ectoderm, and at these points the pores are formed. They open into 

 the ectodermal cavities between the suckers (PI. 4. fig. 6, /'o.), and in this 

 \'*ay a free passage is formed to the exterior. The passage formed by the 

 pore itself through the ectodermal layer is, therefore, extremely short. 



On the ectodermal side the pores are thickly lined with colunniar cells, 

 whose numerous rounded nuclei lie internal to a clear border, containing 

 only an occasional nematocyst (PI. 4. fig. 6). On the endodermal side the 

 cells are shorter and the nuclei larger. A larae increase of endodermal cells 

 is present adjacent to the pores, and through these the passage has been 

 formed to the interior of the body-cavity. The endodermal passage is 

 therefore much longer than the ectodermal. 



Gonads. — No gonads were present in the two specimens examined. 



Development. — The larval form examined had twelve tentacles and twelve 

 perfect mesenteries. Of these the eight primitive Edwardsian septa were 

 alone complete. The four unattached mesenteries are fully developed and 

 possess muscle-pads and mesenterial filaments. This shows a variation in 

 the development of mesenteries and tentacles as compared with the larval 

 stage of a species of a closely allied species, viz. Halcamim duodecimcirrata, 

 described by Carlgren (14, p. 42). Carlgren found that larval forms possess- 

 ing twelve tentacles had all twelve mesenteries attached in the upper part of 

 the oesophagus, and were at that stage already in possession of some mesen- 



