152 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [446] 



of the branchial sac ; these chains are often a foot or even a foot and a 

 half long, and contain two rows of individuals, which are united to- 

 gether in such a way that they stand obliquely to the axis of the chain, 

 the branchial openings being all on the upper side of the chain as it 

 floats in the water, while the posterior openings are all on the lower side 

 of the chain, close to the edge. Each individual is connected both with 

 its mate on the right or left side, and to those immediately in front and 

 behind on the same side. The succeeding individuals in the chain over- 

 lap considerably. The chains do not appear to break up spontaneously, 

 but when broken apart by accident the individuals are capable of living 

 separately for several days. The chains, when entire, swim about quite 

 rapidly by means of the streams of water passing out of all the cloacal 

 orifices in one direction. The individuals composing the chains, when 

 full grown, are about three quarters of an inch long. They are transparent 

 and white, or pale rose, often with the edges of the mantle and the 

 nucleus bright Prussian blue, and with delicate reticulations of the 

 same blue over the surface of the mantle. Each of the individuals in 

 the chains is hermaphrodite, and each produces a single egg, which de- 

 velops into an embryo before it is discharged, and finally when it grows 

 to maturity produces an asexual individual, which is always solitary, 

 (Plate XXXIII, fig. 254.) These are larger than those in the chains 

 and are quite different in form, but the color is the same. These when 

 mature produce, by a budding process in their interior, a series of mi- 

 nute individuals united together along a tube into a small chain, (s, lig. 

 254,) which may be seen coiled up around the nucleus. The chain con- 

 sists of three sections, those individuals in the section first formed being 

 largest and nearly equal in size ; those in the next much smaller ; while 

 new ones are just forming at the other end; as the chain grows longer, 

 and the component individuals larger, it projects more and more, and 

 finally the end protrudes from an opening in the tunic, and the little 

 chain becomes detached and is discharged into the sea. These chains 

 consist of twenty to thirty pairs of individual zooids. This operation is 

 frequently repeated during the summer, and these chains of all sizes, 

 from those just liberated up to the full-grown ones, may be taken at the 

 same time. They appear to grow very rapidly. Thus by autumn these 

 Salpw became exceedingly abundant, at times completely filling the 

 water for miles in every direction, from the surface to the depth of sev- 

 eral fathoms, and are so crowded that a bucket of water dipped up at 

 random will often contain several quarts of Salpce. They were found in 

 wonderful abundance on September 8, off Gay Head and throughout 

 the outer part of Vineyard Sound, and on several other occasions were 

 nearly as abundant. 



Two species of Appendicularia and a species of Dollolum were also 

 found in these waters by Mr. A. Agassiz, but we did not observe them. 

 These are also free-swimming Ascidians, related to Salpa, but very dif- 

 ferent in form. 



