290 JAMF.S RANKIN, 



Tunicate Appendicularia, do exhibit a segmentation of the muscles of 

 the hinder part of the body wall similar to and identical with that of 

 Amphioxus". 



Hkudman in his article "Tuuicata' iu the same edition of the 

 Encyc. Brit., states that the tail (of Appendicularia) "shows distinct 

 traces of metameric segmentation, having its muscle bands broken u\) 

 into myomeres, while the nerve cord presents a series of enlargements 

 from which distributory nerves are given otf". 



It is eviilent that Lankestkh's conclusions from his examination 

 of F. furcata cannot apply to the whole group, as Fol ^) states 

 (speaking generally of the caudal nerve) : "II présente un nombre 

 variable (20 à 40) de renflements de chacun desquels partent de 

 petits filets nerveux se rendant aux muscles et à Tépiderme." 



In F. furcata Seeliger found 10 apparent segments iu the 

 caudal musculature, and 8 of the so-called ganglia iu connection with 

 the nerve cord. I do not think it probable that he is right in re- 

 garding each muscle segment as "eine einzige riesige Muskelzelle", 

 or in stating that "die Segmentgrenzen sind lediglich die Grenzen 

 zwischen zwei Zellen". My reasons will be given further on. 



While working sometime ago, through the kind permission of 

 Dr. Murray, Edinburgh, in the temporary Marine Station at Millport 

 on the Firth of Clyde , 1 found Appendicularia extremely plentiful, 

 and I had abundant opportunity both then and afterwards of examining 

 living and prepared specimens. I found at that time only a single 

 species, viz, Oikopleura dioica. Subsequently I procured from Naples 

 some preserved examples of F. furcata. My attention was specially 

 drawn to the tail of 0. dioica, and from my observations I found it 

 impossible to admit that its structure could l)e interpreted as showing 

 metameric segmentation^). 



1) Études sur les Appendiculaires du détroit de Messine, 1872. 



2) Die Entwicklungsgeschichte der socialen Ascidien, in : Jenaische 

 Zeitscbr. Naturwiss., V. 18, 1884—85. 



3) Some difficulty was experienced in getting a mode of treatment 

 which would bring out cleariy the structure of the tail of these animals. 

 Htftmatoxylin followed by safranin gave good results. Seilek's process 

 I borax carmine followed by .sulj)liiudigotate of soda) gave some fine 

 preparations. When tail.s were treated according to Seiler's method, 

 and afterwards subjected to the action of .safranin in order to intensify 

 the nuclear .stain , extremely good preparations were obtained. The 

 fixing agents used were mercury bichloride, and Kleinknbeko's picro- 

 sulphuric. 



