On a neio Type of Gompound Eye. 233 



at each end, and those of Petromyzon are often (especially 

 in very fresh specimens !) irregular in outline. 



We thus find that the blood differs in almost every point 

 in these two animals, viz. in the size and shape of the red 

 corpuscles and in the character of their nuclei, and that 

 Petromyzon in these respects stands alone, while Myxine 

 resembles other fishes, and especially the Ehismobranchs and 

 Dipnoi, whose corpuscles are much larger than those of 

 Teleostei. But the two genera agree in the extraordinary 

 number of the white corpuscles, which in most fishes are, if 

 anything, exceptionally scanty. 



I did not take the opportunity of estimating the number of 

 the red corpuscles in either case ; but they are certainly 

 exceptionally few, especially in Myxine. 



One very curious point still remains. Shipley, in his recent 

 paper on the development of Petromyzon (Quart. Journ. Micr. 

 Sci., Jan, 1887), states, without further remark, that the red 

 corpuscles of the Ammocoete (P. jluviatilis) are oval ; and in 

 writing to me he confirms the statement that the corpuscles 

 of the Ammocoete difi'er altogether in size and form from 

 those of the adult Petromyzon. This observation is, I fancy, 

 quite novel, and it recalls the similar but far less striking 

 fact that the corpuscles of the young tadpole were long ago 

 observed (by Gulliver) to differ somewhat in size and shape 

 from those of the frog. But the noteworthy point now is that 

 Myxine possesses red corpuscles similar to those not of the 

 adult, but of the larval lamprey, which in many ways it 

 resembles otherwise. 



XXV. — Note on a new Type of Gompound Eye. 

 By F. E. Beddard, M.A., F.Z.S. 



The minute structure of the eye in the Cymothoidas has been 

 treated of by Johannes Miiller *, and more recently by J. F. 

 Bullar t ; the observations of the older author principally 

 concern the cuticular lenses and the vitreous body, and are 

 immaterial to the present note. Bullar has described and 

 figured the eye of Gymothoa in some detail ; his results on 

 the whole show no great difference from the eye of PorcelUoy 

 which has been investigated by Grenacher and described in 



* Meckel's ' Archiv,' 1829. 

 t Phil. Trans. 1878. 



Ann. & Mag. N. Hist. Ser. 5. Vol. xx. 16 



