ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 747 



greenish granulations ami a large nucleus ; they fcjrm groups of four 

 cells, which alternate with the large secreting club-shaped cells. These 

 are fixed to the wall by a filamcutar extremity, and are sui)ported by the 

 neighbouring parietal cells ; the free end dilates into an ovoid head, and 

 is supported by its neighbours, the whole torining a villosity which 

 projects into the cavity of the stomach. These giant-cells have a 

 graniilar protoplasm and a large basal nucleus ; in addition there are 

 other masses in the interior, which vary with the cell under examination. 

 Sometimes there is a rounded body staining with carmine, or the body 

 may be larger and brownish ; in other cases, there are two brownish 

 globes which ajipear to be formed by the transverse division of a single 

 body ; and in other cases there is a rounded grouj) of brownish spheres 

 of which there may be as many as eight or ten. The excretory organ 

 has its wall lined by a layer of pavement-cells, filled with fine yellowish 

 granulations ; these are set free by the breaking up of the cells, the 

 debris and nuclei of which are found among the free granulations. 



Halacaridae.* — Dr. H. Lohman has a monograj^hic memoir on these 

 marine Arachnids. After detailing the history of our knowledge of 

 the group, the author discusses its morphological and anatomical 

 characters, and its systematic position ; a convenient table is given, in 

 which the form of the body, the skeleton of the body, of the legs, and 

 of the capitulum, and other anatomical characteristics are enumerated 

 under the Prostigmata, peculiarities common to the Trombidiidte, 

 Hydrachnida, and HalacaridaB, peculiarities special to the Halacaridfe, 

 peculiarities which they have in common with the Hydrachnida, and 

 those that tbey have with the Trombidiidte. The conclusion arrived 

 at is that the Halacarid8e form a subfiimily of the Prostigmata allied 

 to the Hydrachnida. 



In the systematic portion the subfamily is defined, and the group 

 divided into four genera, of which Aletes and Agaue are new, the two 

 others being Halacarus and Leptognathus. The genera and species are 

 next systematically described ; of the latter there are twenty, ten of 

 which are new. 



In the fourth division of his memoir the author deals with biological 

 results ; these are treated of under the heads of distribution, and 

 peculiarities of mode of life ; the latter is divided into : relation to 

 external influences, where we note that these creatures have a remark- 

 able want of sensitiveness towards cold ; movements of the animals ; and 

 relation to other plants and animals. In the fifth part the ova and the 

 developmental stages are described ; there is a remarkable resemblance 

 between the larvfe and the imagines. 



Structure and Development of Eye of Limulus-t— Mr. S. Watase 

 has a preliminary notice on this subject. When he compares his results 

 with those of Lankester and Bourne, he finds that they seem to have 

 overlooked the existence of one large ganglion cell in the centre of each 

 ommatidium of the lateral eyes, which, in the author's opinion, is the 

 most important morphological element. By using the depigmenting 

 process they failed to make out the important differentiation into the 

 pigmented and non-pigmented parts existing in each rod-bearing cell, or 

 in the retinula. What they have called the intrusive connective tissue 



* Zool. Jahrb., iv. (1889) pp. 269-408 (3 pis.)- 

 t Cnc. Jolm Hopkins Univ., viii. (1889) pp. 34-7. 



