978 SUMMARY OF CURRENT RESEARCHES RELATING TO 



about 200 per minute. Ellipsoidal blood-corpuscles were here and 

 there detected. The circulation is probably effected by energetic 

 peristaltic contractions of the hepatic tubes of the midgut, and of the 

 Malpighian tubes. The heart lies in the anterior portion of the 

 abdomen. 



b. A similar heart was observed in Ixodes ricinus in nymphs 

 and young females. It lies below the posterior margin of the dorsal 

 shield, above the union of the two median diverticula of the midgut. 

 The pulsations and the position of the clefts were detected, and the 

 passage of blood along the aorta. 



c. The heart of Phalangidae is then described. It possesses two 

 pairs of lateral clefts and has no posterior opening. It lies, as in the 

 above, in the anterior abdominal region. With this the heart of 

 Cyphophth alums duricornis is compared. 



d. Herr Winkler also describes the heart of Chernetidns, which 

 has not been previously observed. In young forms of Obisium silvati- 

 cum a long heart was seen lying in the first three abdominal segments. 

 There is, however, only one pair of clefts at the very posterior end. 

 The contractile function appears to be restricted to the posterior 

 portion. Towards the aorta, as in Phalangidaa, the heart appears to 

 be separated off by a valvular fold. There is no strongly developed 

 annular muscle as in Phalangidae. 



The single pair of clefts, the marked reduction of the posterior 

 portion of the heart, the narrowing and slight pulsation of the anterior 

 region, seem to mark the heart of the Chernetidae as a transition type 

 between the elongated hearts with several clefts and the reduced 

 forms in Gamasidaa and Ixodidae. 



€. Crustacea. 



Metamorphosis of Homarus americanus.*— Mr. J. A. Kyder 

 finds that no ecdysis takes place on the hatching of the American 

 lobster : the thin transparent membrane then thrown off being merely 

 an egg-membrane. The first ecdysis takes place from three to six days 

 after hatching, and the first of the seven stages lasts till this time. 



During the first stage, as in the following three, the larva is essen- 

 tially a Schizopod, and without abdominal appendages. The larva 

 swims by means of the exopodites of the last six thoracic appendages, 

 the endopodites being merely prehensile. The telson is triangular, 

 with strong spines. During the second stage, the second to the fifth 

 abdominal aj>pendages appear. Then between the tenth to fifteenth 

 day the second ecdysis occurs, and the third stage is entered upon, when 

 the sixth abdominal appendages make their appearance as biramous 

 lamellae. The third ecdysis takes place by the fourteenth to eigh- 

 teenth day, and the fourth stage is reached, when the appendages arc 

 stronger, but otherwise the larva is similar to the preceding stage. 

 At the end of the third week another ecdysis occurs, leading to the 

 fifth stage. The animal now closely resembles the adult, and the 

 schizopodal character of the thoracic appendages has disappeared, the 



* Amer. Natural., xx. (188G) pp. 739-42. 



