ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 565 



the oldest block, the most proximal zooids are larger than the most distal 

 ones ; in the youngest, the distal ones are larger than the proximal. 

 S. zonaria-cordiformis has "no intermediate piece" or " terminal rem- 

 nant," and the segmentation at the base is not interrupted by an 

 unsegmented portion. The zooids of the blocks are smallest at each 

 end, the maximum occurring near, but not at the distal end. S. cylindrica 

 has an intermediate piece. The zooids are smaller at each end of the 

 block, and the maximum size occurs near, but not at the distal end. 

 These results suggest that further investigation may show the graph of 

 the block to be a reliable species character. The stalk of Equisetum 

 robustum has shorter inter nodes at the base and at the tip, the maxi- 

 mum ones occurring near the base. The diameter of the internodes is 

 least at each end and greatest in the middle. An unusually small zooid 

 is often found opposite an unusually large one in the salpa chain. 



The conclusions reached of a more general or theoretical character 

 are : The periodicity occurring in the salpa chain may be a phenomenon 

 comparable with the grand period of growth, and also with the length 

 period of the internodes, as defined by botanists. ' R. Pearl's first law 

 of growth finds a parallel for the salpa chain, since the size of a zooid is 

 a function of its position in the block. 



INVERTEBRATA. 



Mollusca. 

 a. Cephalopoda. 



Follicular Epithelium of Cephalopods.* — C. Saint-Hilaire gives 

 an account of the minute structure of follicular epithelium in Eledone, 

 Loli/jo, and Sepiola, which is remarkable for the complex system of 

 intra-cellular ducts, previously referred to as vacuoles. 



7» Gastropoda. 



Luminosity of Phyllirhoe bucephala. | — E. Trojan has made a 

 study of Phyllirhoe bucephala Peron and Lesueur, with special reference 

 to its luminosity. As far as is knowu, this is the only Pteropod which 

 is luminous in itself. Two kinds of glandular cells occur in the skin of 

 P. bucephala — mucous cells and albumin gland-cells. The former tend 

 to form many-celled glands, the latter always remain isolated. _ The 

 animal has chromatophores with numerous pigment-granules. These 

 function in the same way as those of Cephalopods. There are peculiarly 

 large mucous glands on the lips of P. bucephala, and it may be that 

 these replace the salivary glands of other forms. This mollusc possesses 

 both single-celled and many-celled skin sense-organs, the latter showing 

 some resemblace to the sensory buds of lower Vertebrates. Luminosity 

 is only observable after stimulation. It is of two kinds : a weak light 

 diffused over the whole body and including the tentacles, and a more 

 intense light restricted to definite poiuts, which are absent altogether 

 from the tentacles and the tail, and most frequent in the latter third of 



* Zeitschr. wiss. Zool., xcv. (1910) pp. 316-26 (1 pi.). 



t Arch. Mikr. Anat., lxxv. (1910) pp. 473-518 (2 pis. and 4 figs.). 



