94 Mr. E. Ray Lankester's Zoological Observations 



tracts in the latter specimens were obvious enough, since 

 they form a reticulate arrangement of ridges, and the corjpora 

 lutea marked these tracts also ; but no cells which were dif- 

 ferentiated as ova were present. Some persons have been 

 inclined to regard these specimens as males ; but I consider 

 this merely a temporary condition of the ovary. In some 

 ovaries, at intervals, large white spherical masses containing a 

 quantity of small cells were found ; these Avere the most 

 likely indication of testicular organs which I succeeded in 

 finding. The appearances of the ovary in various conditions, 

 and the structm-e of the mantle (in which I could not identify 

 the numerous layers distinguished in Waldheimia Jlavescens 

 by Mr. Hancock, in his great essay on Brachiopoda) , require 

 illustrations for a fuller explanation. 



Phyllirrhoe bucephala and Mnestra. 



Perhaps the most charming of all the objects which the 

 Naples Bay affords to a zoologist of histological tendencies is 

 the curious little fish-shaped mollusk Phyllirrhoe. Its trans- 

 parency is perfect, at the same time that the tissue-elements 

 present definite outlines. Its anatomy and histology are well 

 enough known from Heinrich Miiller's paper. The pulsating 

 heart — lying in the small pericardium which communicates by 

 a long partly ciliated tube (the representative of the organ of 

 Bojanus) with the exterior — is an object of intense interest. 

 It was easy to trace the connexion of the finest nerve-twigs 

 with muscular fibres and with various peculiar corpuscles. 

 Prof. Panceri discovered, whilst I was at Naples, that these 

 corpuscles, as well as the nerve-ganglia, are phosphorescent. 



Krohn described, some thirty years ago, a medusoid which 

 presents the remarkable character of being parasitic on Phyllir- 

 rhoe. I obtained specimens of this, but have no indication of 

 the way in which it becomes attached. The tissue of the me- 

 dusoid's disk appears to hejiised at its middle aboral point with 

 the tissues of the Phyllirrhoe. It cannot be removed without 

 tearing, and always occurs just below the chin (if the term be 

 allowed) of the Phyllirrhoe. I made out (and have drawings 

 of) a circular and four radiating canals, four marginal tentacles, 

 abundance of thread-cells, and a central chamber. 



Pyrosoma, ^ginopsis, and Cercaria. 



Prof. Panceri and his assistants were carrying on their valu- 

 able investigations on the embryology and phosphorescence 

 of Pyrosoma whilst I was staying at Naples. In December we 

 obtained a good supply of these most interesting Tunicates. 



I directed my attention chiefly to the early changes in the 



