SALPA — DEVELOPMENT OF THE ORGANS IN" THE BUD. 509 



connection with the development of the organs in the bud are thos< 



of Salensky (Nos. 101 and 102) and Seeliger (No. 105). Although 

 the researches of these investigators yield much valuable material for 

 working out the organogenesis of the buds of Salpa, yet, owing to the 

 fad that these observers did not recognise the rotation of the bud 

 round its longitudinal axis, as made out by Brooks, their observations 

 are somewhat vitiated through the adoption of an erroneous orienta- 

 tion of the bud, taken from its later stages and applied in describing 

 the earlier stages. Salensky and Seeliger hold that the buds 

 arise simply by the lateral shifting of the segments of the stolon. 

 According to them the dorsal part of the bud develops from one of 

 the lateral surfaces of the stolon, while its ventral side corresponds 

 to the opposite side of the stolon. According to Brooks, on the 

 contrary, the right side of the stolon gives rise to the right half of 

 the body of the bud and the left side of the stolon to the left half. 

 In the following account we shall merely give a brief outline of the 

 genesis of the organs in Salpa which probably closely rese'mbles that 

 in Pyrosoni't * 



It must once more be pointed out that we have the first rudiment 

 of the bud in a transverse segment of the stolon. The proximal 

 parts of this segment become the dorsal side of the bud, and the 

 distal parts its ventral side. From the upper region of the stolon is 

 developed the anterior part of the body of the bud, while its posterior 

 end develops from the lower region (see diagram, Fig. 268). The 

 organs of the bud are formed from sections of the tubes and longi- 

 tudinal strands which are to be seen in the transverse section of the 

 stolon (Fig. 265). 



That part of the central entoderm-tube found in each segment of 

 the stolon gives rise to the pharynx of the bud. The entoderm-tube, 

 iii a cross-section through the stolon, bears some resemblance to the 

 expanded wings of a butterfly (Fig. 264 6'). an upper and a lower 

 indentation and two lateral indentations beim>- found in it. Its form, 

 in cross-section, later resembles that of the letter H, also found in a 

 similar section of a Pyrosoma bud (Fig. 257). In the latter, the two 

 portions of the tube that point upward arc connected with the 

 development of the endostyle-folds, while those that extend down- 

 ward, yield the stomach and intestine (p. 1 ( .»0). It is at present 

 impossible to say whether similar conditions prevail in tin- Salpa bud. 



* [Brooks' memoir on the geuus Salpa (No. I.) should be consulted in this 

 connection ; he gives a full and detailed account of the development of the 

 chain-form, including its organogenesis. — Ed.] 



