lOOLOaY AND BOTANTj MICROSOOPYj ETC. 45 



flagella. The hypoganglionic gland is neither mucous nor renal in func- 

 tion, and its true significance still remains to be discovered. As to the 

 morphological character of the gland and of the vibratile organ, the 

 author is inclined to think, with Eoule, that Julin is right in regarding 

 them as homologous with the hypophysis of Vertebrates. Before com- 

 mitting himself to this he would, however, like to see the organ in 

 Amphioxus which is homologous with the hypophysis. 



The eighth chapter deals with the muscular system, which is exceed- 

 ingly well developed in Fragaroides. The longitudinal muscles are all 

 lateral, and are inserted into an epidermal projection, the cells of which 

 are specially modified. There are twenty longitudinal muscles on either 

 side of the body. The transverse muscles of the gill have a number of 

 anastomoses with the longitudinal. Around the buccal and cloacal 

 orifices there are circular muscles, and the anus is provided with a 

 sphincter. Each muscular bundle is made up of homogeneous fibres, 

 which bear no traces of transverse striation. The fibrils are separated 

 from one another by a protoplasmic mass in which are nuclei, and the 

 whole is invested by a sarcolemma. They are of a mesenchymatous 

 nature, although the Ascidians are enterocoelic. 



The circulatory system or epicardiac organs form the subject of the 

 ninth chapter. The epicardium is in the form of a w^ide median tube, 

 and dorsally or ventrally to it there is a tubular prolongation of the 

 pericardiac cavity. The heart, which is placed at the extremity of the 

 post-abdomen, is curved and one of its horns is prolonged into the dorsal 

 and the other into the ventral half of the post-abdomen. The membranes 

 of the heart and of the investing pericardium are continuous with one 

 another along a longitudinal cleft which lies on the convex surface of 

 the heart. This cleft remains open and the cavity of the heart is in 

 relation to the blood-lacunge, not only at either extremity of the organ, 

 but along the whole length of the cardiac raphe. The epicardium bi- 

 furcates posteriorly, and then ends blindly. Anteriorly it divides, at the 

 plane of the stomach, into two tubes, the anterior ends of which are 

 applied to the base of the branchial cavity. In the adult no orifices can 

 be detected, but in young larvae there are distinct communications 

 between these tubes and the branchial cavity. The wall of the heart is 

 formed by a simple layer of epithelio-muscular cells, and there is no 

 trace of an endocardium. The circulation of the blood is not effected by 

 the aid of vessels, but through simple lacunte hollowed out in the con- 

 nective tissue ; the blood is transparent and carries a large number of 

 free mesodermic cells which retaia their primitive characters. The epi- 

 cardiac plate plays a very important part in the circulation ; the sac is 

 connected with the wall of the body, and forms a partition which divides 

 the post-abdomen into a dorsal and a ventral half. The two blood- 

 currents are thus completely separated from one another, and the! 

 alternation of the beatings of the heart is of real use in distributing the 

 oxygenated blood to the organs of the body. 



The final chapter contains an account of the reproductive organs^ 

 Fragaroides is hermaphrodite, and the organs, ducts included, are closely 

 connected with one another. The testis is made up of a very large 

 number of lobes, each of which has an excretory ductule which opens 

 into the vas deferens. In each lobe there is an epithelial layer of 

 flattened cells, and an interior mass of rounded cells which become 

 converted into spermatozoa. The ovary appears to begin to function 



