82 PROGRESS OP MICROSCOPICAL SCIENCE. 



genera, and the end of the abdomen rests on the outside of the 

 yolk, rather than rolled in within the yolk ; but that the germ is an 

 endoblast (so far as that condition has any special significance) is 

 shown by the fact that the ventral side of the primitive band points 

 inwards towards the centre of the yolk, as in the Libellulidai, the 

 Hemiptera, and some Coleoptera (Telephorus and Donacia) in contra- 

 distinction to the Phryganeidfe and the Podurje (Isotoma), in which 

 the germ or primitive band floats entirely on the outside of the yolk. 

 After the procephalic lobes and rudiments of the appendages of the 

 head and thorax have begun to develop, a second moult (visceral 

 layer) of the blastoderm is made, which envelops the head and under- 

 side of the body, much as in the Libellulidse and Hemiptera. At this 

 time the embryo is much like that of the last-named insects. The 

 germ does not revolve in the egg, as in the Libellulidse, but the head 

 remains throughout embryonic life next the micropyle. At the next 

 stage observed, the appendages of the limbs had appeared, the em- 

 bryo being situated on the outside of the yolk, the end of the abdo- 

 men curved around on the opposite side of the yolk. At this time the 

 inner or " visceral layer," forming a second moult of the blastoderm, 

 envelops the germ, much as in the LibellulidsB, and Hemiptera, and 

 Coleoptera (Donacia). It is evident that this faltenhlatt of Weismann 

 (or visceral layer of Brandt) is shed at a later stage than the 

 " amnion " proj)er. This stage corresponds with that of Calopteryx 

 figured by Brandt. At this time the germ of Diplax and Calopteryx 

 (Libellulida)) floats within the yolk, but this difference he would regard 

 as having no special importance, as in the Hemiptera the germ at the 

 same stage of development rests on the outside of the yolk in Corixa, 

 while in the Pediculina, according to Melnikow's researches, the 

 germ floats within the yolk, and in the CurculionidaB (Attelabus) the 

 germ rests on the outside of the yolk (ectoblast), while that of Tele- 

 phorus is a decided endoblast, i. e. floats in the interior of the yolk. 

 After this period, the embryo of Chrysopa exactly corresponds to 

 that of all the Libellulidfe whose development is known (Agrion, 

 Calopteryx, Perithemis, and Diplax). The embryogeny of Chrysopa 

 is identical, then, with that of the Libellulidfe. What becomes, 

 therefore, of the distinction between the " Pseudoneiiroptera" and 

 " true " Neuroptera, insisted on by some of the leading entomologists, 

 since Erichson's day? "Never believing that the differences were 

 great enough to separate the Linn£ean Neuroptera into two inde- 

 pendent orders or suborders (whichever we may choose to call them), 

 I now ask if embryology does not give independent testimony as to 

 the close alliance at least of the Libellulidae and Hemerobidse, even 

 if we go no farther ? " 



Relation of BracMopoda to Polyzoa. — In his recently-published 

 memoir on the ' Early Stages of Terehratulina sepientrionalis,' Professor 

 Morse thus discusses the relations which exist between the above two 

 groups. With propriety may also be suggested a certain parallelism 

 between the leading groups of the Polyzoa and the Brachiopods. We 

 have forms like Lcpralia, attached by one region of their shell, this 

 Bhcll being calcareous and exhibiting minute punctures, which have 



