404 THE CANADIAN NATURALIST. [Vol. X. 



oesophagus, immedijitely below the epistome. It is easily seen in 

 Pectinntella and presents curious contractions and expansions. 

 By these the position of the mass is altered, sometimes approach- 

 ing nearer the oesophngus, at others being in the hollow of the 

 epistome. Nerve branches may be seen proceeding from this 

 ganglion chiefly towards the epistome and tentacles. 



The muscular system is well developed and the muscles form 

 cither sphincters or elongated branches. A definite sphincter 

 surrounds the orifices of the coenoecium and closes them tightly 

 when the polyps are retracted, relaxing again for their pro- 

 trusion. The longitudinal bands arise from the base of the 

 coenoecium, and passing up are distributed in three difierent 

 localities, on the stomach, the base of the lophophore, and the 

 tentacles, and are called respectively the gastric, lophophoric 

 and brachial retractions. By the action of these muscles the 

 little animal can be instantaneously withdrawn, and the sphincter 

 closing eficctually shields them from injury and attack. Other 

 muscles are described by Hyatt nnd Allmnn, in connection with 

 the epistome and endocyst. 



The Phylactoloemata are reproduced by budding and true ovu- 

 lation. From the side of the polyps buds arise which develope 

 into mature forms and in this way the colonies are increased. 

 Another method of budding results in the production of free 

 gemmae or statoblasts, which arise from the funiculus. These 

 present a horny sheath, usually dark brown in colour, and 

 an annulus or margin, which in some species is provided with 

 spines. In Pectinatella, the spines number from 12-20, in 

 Cristatella there is a double row, one shorter, the other 

 longer, 50-60 in all, and the extremities are furnished with from 

 4-6 booklets. The statoblasts float on the surfiice of the water 

 and the armed ones get entangled in the weeds. 



The method of production of true ova was first described by 

 Allman. They originate in a bud-like mass at the upper side of 

 the endocyst and are fertilized by spermatozoa, the testicles being 

 an offshoot from the funiculus. 



In the o;enus Plumatella I have determined three Canadian 

 species, arethusa, vitrca, and diffusa. The members of this 

 genus have dendritic, plant-like coenoecia, which are firmly at- 

 tached to the surf;ice of submerged twigs, stones and water- 

 plants. The coenoecium is composed of little hollow branched 

 tubules, divided into cells, from the apex of which the little polyp 



