ZOOLOGY AND BOTANY, MICROSCOPY, STO. 805 



Development of Astacus.* — The early stages in the development 

 of A. leptodactijlus are, according to M. W. Schimkewitscb, as follows. 

 The germinal disk lies on the upper surface of the egg and is un- 

 ' segmented ; the protoplasmic mass becomes divided into two, each 

 ■with a nucleus ; it then becomes further divided but the boundaries of 

 the cells are lost ; later the portion of the yolk corresponding to the 

 segmented germinal disk becomes divided into pyramids which do not 

 extend as far as the centre of the ovum. Comparing the segmentation 

 of Astacus with Palaemon, it appears that while in the latter the seg- 

 mentation of the yolk keeps pace with the segmentation of the 

 germinal disk, in Astacus the segmentation of the yolk does not 

 commence until after the segmentation of the germinal disk is 

 completed. 



Extraction of Uric Acid Crystals from the Green Gland of Astacus 

 fluviatilis.t — Dr. A. B. Griffiths describes a chemical investigation 

 of the green gland of Astacus fluviatilis resulting in the extraction of 

 uric acid crystals from its secretion. This investigation proves that 

 the so-called green gland is a true urinary organ, its secretion con- 

 taining uric acid and very small traces of the base guanin ; the greeu 

 gland is, therefore, physiologically the kidney of the animal. 



Parasites of Maena vulgaris.^ — M. E. Saint-Loup describes 

 shortly, under the name of Anilucra edtvardsii, a new isopodous parasite 

 which is to be found attached to the caudal fin of Msena vulgaris ; it 

 is distinguished from A. mediterranea by the greater length of the 

 second pair of antennse ; the eyes do not atrophy in the adult. 



On the sides of the allied Smaris vulgaris and in its pharynx there 

 lives a Crustacean very like Cymotlioe oestrus, which is interesting from 

 the fact that the young have the same arrangement of pigment as was 

 noticed by van Beneden in a species of Oniscus. 



Msena is also infested by a polystomatous Trematode, to which the 

 author gives the name of Choricotyle marionis ; it is, perhaps, most 

 interesting on account of the fact that the characteristic " chitinous " 

 hooks on its suckers do not present with picric acid the reactions of 

 chitin. 



Nervous System of Apus.§ — Mr. P. Pelsencer has made a careful 

 investigation of the nervous system of Apus, with the special object 

 of answering certain questions which, in his essay on that form. Prof. 

 Eay Lankester had propounded. 



1 he first of these may be thus stated : Does the swelling from 

 which the antennary nerves issue arise from the fusion of the first 

 and second ganglia ; or have the ganglia of these two appendages dis- 

 appeared ? Mr. Pelseneer finds that tlie elongated ganglionic swelling 

 docs not represent a fusion, and that the two pairs of antennary 

 ganglia arc still very distinct ; nor, as has been thought, has the 

 rnaxillipcdc-ganglion not disappeared. 



• Zr)o). Anz.ei^., viii. (IRSf)) pp. 30:^-4. 

 t I'rfKJ. Hoy. Koc, xxxviii. (188.')) pp 187-8. 

 J G<mii)t(H UciidiiH, ci. (188.0) pp. 175 and (J. 

 § Quart. Jourii. Micr. Sci., xxv. (ISS."}) i)p. iXi-W (1 pi.) 

 8tr. 2. -Vol. V. 3 a 



