Explanation of the Plates, 



Plate I. 

 Rhabdopleura mirabilis. 



Fig. 1. One of the largest connected pieces of a colony found, about 3 times magnified. 

 &. & the creeping stem, from which the single cells arise. 



2. Another, piece, of which the creeping stem is attached on 2 points to extraneous 

 particles, forming between the two a freely hanging bridge. 



3. A part of a living colony magnified about 16 times, a. a, the cells with their po- 

 lypides in different states of protrusion; b. b, the creeping stem; c. c, the bucal 

 shield; d. d, the tentacular arms; f. /j the stomach; g, the intestine; h. h, the con- 

 tractile cord; i. i, the axial cord. 



4. The extremity of a cell, with its animal protruding from the aperture, strongly mag- 

 nified, a, the cell; c, the bucal shield; 'd.d, the tentacular arms, which here are 

 strongly curved outwards and downwards. 



5. The animal taken out of its cell, c, the bucal shield; d, the tentacular arms; e,. 



the oesophagus'; the stomach; g. the intestine; A, the spirally coiled contractile cord. 



6. The lower end of the contractile cord, still more strongly magnified, shewing every- 



where its evidently cellular structure. 



7. A piece of the contractile cord about in the middle of its length, very strongly 



magnified, shewing in the dorsal part a cellular structure, and in the ventral part 

 a fibrous or muscular structure. 

 8. One of the tentacles also very strongly magnified. 



9. A piece of the creeping stem, freed from the adherent extraneous particles, shewing 



the irregular arrangement of the circular rings, i. i, .the axial cord. 

 10. A longer piece of the creeping stem, likewise freed from the adherent particles, 

 together with the basis of the cells with their polypides mostly strongly retracted, 

 about 20 times magnified, shewing the single chambers into which the stem is di- 

 vided, c. c, the bucal shield; f. f, the stomach; h. h, the contractile cord; i.i, the 

 axial cord. 



11. A small piece of this stem, together with the basis of a cell strongly magnified, 



shewing the attachment of the contractile cord, and one of the transversal septa. 



