300 NOTES AKD MEMOEANDA. 



loped ; tliese consist of one or more tufts of a large number of short 

 ramules ; their function appears to be to supply the organism with air 

 during such short periods as those in which respiration is prevented 

 or retarded ; the hairs are better developed on the side nearer to the 

 respiratory tubes than on the other. Very much the same relation of 

 parts is found to obtain in the pupa. 



In the imago the conditions appear to be altogether different ; the 

 insect now respires by the aid of stigmata. The hairs on these struc- 

 tures are described in some detail, and the descriptions illustrated. 



Sucking Plate of Dytiscus. — The same author describes * the chiti- 

 nous organs on the sucking plate on the first pair of feet in the males 

 of Dytiscus. These, wLich aj^pear to be of aid in copulation, are 

 formed by the differentiation of the first joints ; in coi^ulation they 

 are apjilied to a shallow groove on the thorax of the female ; they are 

 cordiform in shape, and are formed from throe of the joints of the 

 tarsus ; in colour they are more or less red or brown, and on their 

 upper surface they present a roughened, file-like surface, which is 

 pi'oduced by the presence of a number of rounded, flattened organs, 

 some of which may be easily perceived by the naked eye. In some, 

 the structure is remarkable on account of the presence of radiating, 

 yellowish, and branching chitinous hairs, separated by a colourless 

 transparent membrane, which is more or less distinctly striated ; on 

 the inner surface of these organs there are roimded bodies which 

 produce a dark brown secretion, the function of which appears to be 

 to protect the bodies in question against the action of water. In 

 others there are several transverse rows of smaller bodies ; these 

 consist of a single hollow chitinous hair, which is closed at its tip ; 

 this again is jirovided with a transparent chitinous membrane of a 

 brownish hue. Adding together all the prehensile structures observed 

 on these appendages, the author comes to the conclusion that there are 

 no less than four hundred of them, the power of which is at once 

 apparent. The plates now described are provided with a number of 

 hairs of two kinds ; in one they are long, firm, blunt, and curved a 

 little inwards, so as to afford a protection for the subjacent struc- 

 tures ; the others are broad and short, are distinctly striated in a 

 longitudinal direction, and are inserted into strong chitinous rings. 



Development of Polyzoa. — M. W. Eepiachoff, of Odessa, has 

 studied the development of Tendra zostericola,^ of Lepralia palla- 

 siana, and of two sj)ecies of BoioerhanJcia.^ In Tendra complete yolk- 

 division takes place, and an equal-celled mulberry-mass (archimorula) 

 is produced, which soon becomes hollow by the formation of a 

 cleavage cavity, producing a one-layered archiblastula. Four cells 

 lying together in the centre of the ventral side, then enlarge greatly, 

 and undergo extensive division, forming a mass of cells projecting 

 into the cleavage cavity. This mass is the endoderm ; its cells soon 

 separate from one another, forming a cavity, the archenteron, which is 



* 'Arch. f. Naturgeschichtc,' xliv. (1878) 9]. 



t ' Zeitsch. f. wiss. Zool.,' vol. xxx. Suppl. (1878) 411. 



X ' Zool. Anzeiger,' i. (187S). 



