258 MR. F. J. COLE OlSr THE DBVELOPilENT OF 



Thomson, with a statement that he did " not consider it a com- 

 pound Ascidian, but rather an aberrant Polyzoan related to 

 Bhaldopleura:' As a result the animal was at once forwarded 

 to the late Mr. George Busk, and after that to Prof. Mcintosh, 

 as stated by the latter in the ' Challenger ' report on Gephalo- 

 discus (p. 3). The material I have used is a few fragments made 

 use of by Prof. Herdman in his first determination of the probable 

 aflfinities of the animal. 



As described by Professor M'Intosh in his ' Challenger ' 

 report, the branchial plumes " are nearly of uniform size, and 

 consist of a tbiokish central stem, occasionally slightly crenate, 

 and furnished with a series of longitudinal fibres ; while distally 

 each is terminated by a peculiar bulbous enlargement, which at 

 first sight resembles the tip of certain hydroid tentacles (e. g. 

 Coryne or Syncoryne) bristling with dart-cells and pigment. 

 The rugose appearance, however, is due to large gland-cells 

 containing granules and globules, which are arranged in a some- 

 what regular manner round a central cavity, and which present 

 a deep yellowish tint in the preparations. This structure may 

 perhaps be a further and special development of the somewhat 

 large hypodermic granules of the tips of the pinnae." Elsewhere 

 Mcintosh states that the bulbous enlargements of the plumose 

 arms may secrete the " spinous processes or fimbriae " on the 

 surface of the ccenoecium. Although Mcintosh did not succeed 

 in elucidating the nature of the "large gland-cells," his description 

 above, as far as it goes, and excepting perhaps the last statement, 

 is quite correct. 



Masterman's interpretation of the bulbous enlargements 

 (which may be conveniently termed " rhabdite-batteries ") is 

 that they represent " a dozen large eyes of a very primitive 

 compound type." As this conclusion is so directly opposed to 

 the explanation given in this paper, it is perhaps as well that 

 the evidence on which it is based were summarized. It is as 

 follows : — 



1. " If the parts be subjected to partial maceration the clear 

 globules [inside the gland-" cells "] can be obtained free, 

 and they remind one irresistibly of a crystalline refractive 

 lens." 



