LIST OF ILLUSTRATIONS xxxi 



FIG. PAGE 



561. Anatomy of dipneumonous Spider . . . 653 



562. Limulus, sagittal section .... . 654 



563. Book-lung of spider ... . . 654 



564. Tracheal system of Spider . G55 



565. Book-gill of Limulus .... 655 



566. Lateral eye of Euscorpio. . 655 



,567. Central eye of Euscorpio . 656 



568. Nymphon hispidum ..... . . 657 



569. Pentastomum taenioides ; ... 658 



570. Macrobiotus hufelandi .... . . 658 



571. Diagram to illustrate affinities of Arthropoda . . 661 



572. Anodonta cygnea . 664 



573. ., .. interior of valve and animal removed from shell . 665 



574. ,, ., section of shell and mantle . . . . 666 



575. .. ., animal after removal of mantle-lobe . . . 667 



576. .. ,. dissection from left side . . . 668 



577. ,. .. structure of gills .... . 669 



578. .. ,, transverse sections ... . 670 



579. ,, diagram of circulation .... . 672 



580. ., statocyst . v - 673 



581. .. early embryo . . 674 



582. ,, later embryos .... .... 675 



583. ,. advanced embryo . 675 



584. ,, metamorphosis . 676 



585. Anatomy of Pecten ..... . 679 



586. Valves of Mya, Mocliola, and Vulsella . . . 680 



587. Cardium edule . . 680 



588. Venus gnidia . .681 



589. Scrobicularia piperata ..... . 681 



590. Solecurtus strigillatus ... . 682 



591. Diagram of concrescence of mantle-lobes . . 682 



592. Requienia and Hippurites .... . 683 



593. Teredo iiavalis . . 683 



594. Aspergillum . . - 684 



595. Mytilus edulis . . 684 



596. Nucula delphinodonta ... . 684 



597. Gills of Pelecypoda . . 685 



598. Gill-filaments of Mytilus . 686 



599. Dissection of Poromya ... . 686 



600. Donax, enteric canal .... . 687 



601. Nervous system and auditory organs of Nucula 688 



602. Eye of Pecten . . - 689 



603. Development of Ostrea . . 690 



604. Veliger of Ostrea . . .691 



605. Embryos of Cyclas . . . - 691 



606. Diagram illustrating the mutual relationships of the Pelecypoda. 693 



607. Chsetoderma nitidulum 695 



608. Neomenia carinata . 695 



