apb.il — sept. 1858.] Order lladiata. 137 



The order of the " Cylinder-sheaths" or Salpoe (Biphora)l'em- 

 braces swimming animals of glassy transparency which are parti- 

 cularly numerous in warm seas. The greater part of the body is 

 formed of a gill-bag, often furnished with extraordinary points and 

 appendages : — it clearly consists of an outer and an inner cover- 

 ing, in which are placed bundles, or oblique bands of muscular 

 fibres. The digestive organs and the heart are pressed together 

 into a little round ball which has been called the kernel or 

 nucleus : — this is generally red or yellow, seldom blue, and shines 

 by night with a lively reddish-yellow lustre. At the fore-end of 

 the cylinder-shaped body is an oblique opening surrounded by 

 moveable lips which leads into the wide gill-bay. The ganglion 

 with its nerves radiating in all directions is very distinct, as is also 

 the eye surrounded by a dark brownish red colouring matter which 

 is placed on it. On the lower side of the gill-bag there is a groove 

 set with cilise, and a wrinkle also ciliated near the mouth, the 

 uses of which are not yet known. 



The Biphora are found swimming in various social stages. Ge- 

 nerally they form chains, in such a manner that long rows of indi- 

 viduals are attached to each other by the pointed prolongations of 

 their bodies or by their sides, so that one sees a long band swim- 

 ming in the sea, set with a quantity of red nuclei in alternate rows. 

 All the animals inhale and exhale water at the same time and thus 

 the chain progresses. An animal which is once separated from the 

 chain (see fig. 10, plate vi.) cannot unite itself to it again, for it clings 

 to its companions only by hardened slime. There are however 

 Salpoe which never form into chains under any circumstances, and 

 which do not agree in their form with the chained individuals. 

 They were formerly considered to be of a different kind, but mo- 

 dern investigations have proved that chained and single individu- 

 als, however they may differ in their outward appearance, are all of 

 one and the same kind in different stages of development. In all 

 the Biphora there is to be found in the neighbourhood of the heart 

 a kind of knot or cone, in which a strong stream of blood rises and 

 falls, and which at first looks very unimportant. After some time • 

 one may see on this cone little wart-like protuberances, which grow 

 by degrees till they form a circle of embryos placed round the cone. 

 Vol. xx o. s. Vol. iv. n. s. 



