REPORT ON THE SIPHONOPHORJE. 155 



of the first nectophore. Along its dorsal side runs the nectocalycine duct or pedicular 

 canal (cp), which opens at the apex into the top of the stem. 



Hydrcecial Canal. — Whilst the dorsal half of the basal nectophore is occupied by the 

 slender, cylindrical, slightly curved nectosac, its ventral half is occupied by the hydrcecial 

 canal (nf). This is an open groove in the greater part of its length, limited by two 

 \ riitro-lateral wings of the umbrella ; but in the middle part (opposite to the superior 

 third of the nectosac) the two wings have grown together and form a complete canal 

 (figs. 4, 5 nb,), and in the inferior third the broader left wing (nl) overlaps the smaller 

 right wing (nx). The five denticulate edges of the second nectophore and the five basal 

 teeth around the mouth correspond to those of the first. 



Siphosome (fig. 1, a).— The common stem of the body is a very long and slender 

 tubule in the expanded state, four to six times as long as the nectophores. It is enclosed 

 in the hydrcecial canal of the basal nectophore, is attached at the apex to the top of the 

 hydrcecium of the apical nectophore, and is here directly prolonged into the somatocyst 

 of the latter (cs). Whilst a great part of the siphosome can be retracted into the 

 hydrcecial canal when contracted perfectly, it can be widely prominent by its lower 

 aperture when expanded. 



Cormidia. — The eudoxomes, which beset the whole stem at regular intervals (about 

 equal to their lengths) are very numerous, in large specimens sixty to ninety, or more 

 (fig. 1 ). They have a spathiform bract, which is prolonged above its insertion upwards 

 into a cowl (PI. XXXIV. figs. 9, 11). This cowl is open at the ventral side, and con- 

 tains a spindle-shaped phyllocyst (cs), which encloses in its apex an oleocyst (co). The 

 ventral side of the bract is opened by a deep fissure, and its base obliquely bevelled, 

 and armed with four short triangular teeth ; the two dorsal teeth are larger than the two 

 ventral. 



The cavity of the bract encloses a cylindrical siphon with a long tentacle, and besides 

 a large special nectophore, and one or two, rarely three, gonophores. These are brought 

 to maturity after the eudoxome has been detached from the stem. It then swims 

 freely about as Erssea compressa (compare the description of this genus, pp. 122-124, 

 and PI. XXXIV.). 



Subfamily Abylid.-e. 



Genus 29. Abyla, 1 Quoy et Gaimard, 1827. 



Abyla, Quoy et Gaimard, Ann. d. Sci. Nat. (Zool.), t. x. 



Definition. — Diphyidas with two angular, pyramidal or prismatic nectophores of 

 different size and form. The basal nectophore is three-sided-pyramidal, asymmetrical, 

 and much larger than the symmetrical apical nectophore. Bracts six-sided-prismatic, with 



1 Abyla = Aflfax, the southern column of Hercules, opposite to Calpe, Strait of Gibraltar. 



