392 Prof. J. Reid on the Anatomy and 



body are developed. In the beginning of October I procured 

 several specimens in which a large mass of cells (ova) was placed 

 in the space between the gullet, intestine and upper edge of the 

 stomach (fig. 8 h), extending downwards to the entrance of the 

 gullet into the stomach, and depressing the stomach and forcing- 

 it considerably downwards. In two of these this mass of cells 

 projected into the interior of the gullet near its lower part, and 

 exceedingly minute ciliated ova were seen escaping from the 

 upper part of the cellular mass, and several were also seen swim- 

 ming in the interior of the gullet and stomach. Portions of this 

 mass of cells were after a time extruded outwards, and were com- 

 posed of the ciliated ova, and of very minute nucleated cells con- 

 nected together by a structureless substance. Many of these ova 

 formed a single cell, broader at one end than at the other, with a 

 circle of cilia longer than the cell placed around the margin of 

 the broad end (fig. 9 «), while others presented one, two or more 

 very minute cells attached to its lower or narrow extremity 

 (fig. 9 6 & c) . The nucleated cells consisted of a cell-membrane 

 with two or more nuclei, and appeared to be undeveloped ova. 

 The ciliated ova swam actively about, sometimes bending all 

 their cilia in the same direction, forming a curved bundle and 

 striking in the same line for some time together, at other times 

 spreading their cilia and moving them in different directions. 

 These ova are so minute as to require very high magnifying powers 

 for their examination. It would thus appear that this polype, sup- 

 posing all the individual animals whose stalks are attached to the 

 same creeping stem to form one aggregate animal, extends and 

 prolongs the life of the individuals composing it in two ways ; viz. 

 by renewal of the individual bodies after they have dropt off, and 

 by offsets of new individuals from the creeping stem ; and that it 

 reproduces and extends the species, or forms new aggregate ani- 

 mals, by the formation of ciliated cells. I have never been able 

 to detect any circulation of nutritious juices in the stalk, though 

 examined under the most favourable circumstances. 



Crista chelata. This polype when extruded affords a good 

 view of the membrane connecting the outer sm'face of the pha- 

 rynx and rectum together (fig. 10 a). It would be more correct 

 to say, connecting the supporting part of the tentacula and rec- 

 tum together, for the pharynx, as in the other ascidian polypes, 

 lies loose, and can be seen contracting, within this supporting 

 part. It protrudes itself through a small opening at the upper 

 margin of the cell, and the large opening seen in the dead spe- 

 cimen on the anterior surface of the cell, is in the living speci- 

 men covered in by a membrane. The polype has from ten to 

 twelve ciliated tentacula about half the length of the cell. The 

 dilatation of the digestive tube (stomach) at the termination of 



