Miscellaneous. 481 



then the femnles lay eggs rapicllj' and soon die. This short 

 existence is incompatible with the development of the embryo in 

 the maternal organism. ISor is this rule general : 1 have studied 

 recently a species of the EphemeridiE in which an entirely different 

 state of things prevails ; this is Chloeopsis diptera (Latr.). This 

 species is very common in houses at the end of summer and the 

 commencement of autumn, when these insects attach themselves 

 to the windows or the ceilings, and there rest immovable, their two 

 wings turned back and applied one against the other, the posterior 

 part of the abdomen terminated by two long filaments, turued back 

 upon the dorsal aspect. The same insect may be observed in the 

 same place for several days. Having captured a large number of 

 them, I have been able to keep them for more than three weeks 

 before they laid their eggs. I have found it impossible to fix 

 exactly the duration of their existence, because at the time of 

 capture I did not know how long they had emerged from the 

 nymph state. However that may be, there are Ephemerae which 

 have but little title to the name. This relatively long existence in 

 the ndult state is in accord with their processes of reproduction. 



Desiring one day to study the circulation of the blood in one of 

 these insects, in the living state, which I supposed to be sufficiently 

 transparent for the purpose, I took one of them and placed it 

 between two plates of hollowed glass. The pressure of these plates 

 caused a quantity of greyish matter to exude from the abdomen of 

 the animal ; I regarded the insect as dead and my observations a 

 failure. Nevertheless, on examination with the microscope, I 

 observed that the extruded matter was formed of a great number 

 of little ovoid bodies, which immediately began to move about and 

 unroll themselves. Each of them was a little larva, which was 

 very active and began to swim about. Were these Ephemerae 

 viviparous ? This was the question that I at once asked myself. 

 Then I examined the contents of a large number of individuals, and 

 I found eggs in every stage of development : in some the segmenta- ' 

 tion was but slightly advanced, but a commencement of evolution 

 was very distinct ; in others, the extruded larvae showed segmenta- 

 tion ; the most advanced enclosed completely developed larvge, but 

 still enclosed the transparent membrane of the e^g. I have since 

 been able to observe the females emitting their larvae freely without 

 any pressure, so that their viviparity is a proven fact. When the 

 moment approaches that the insects seek the water, they allow 

 themselves to fall into it and float on the surface, with their wings 

 extended, up to the moment at which the larvae are extruded. 

 During this operation, which lasts for a very short time, the whole 

 of the last three segments of the abdomen are lifted upwards so as 

 to form almost a right angle with the rest of the body. The larvae 

 are expelled by a double orifice pierced between the seventh and 

 the eighth abdominal rings ; these two openings are only separated 

 from one another by a very slight portion of tissue, and generally 

 break into one another so as to become one after the deposition of the 

 eggs ; there results a large slit, which involves the whole of the 

 lower half of the line of junction of these two rings. In this case 



