On the Structure ami Development of Argiope. 513 



the nurober of tentacles g-radually increase to teu. The setae drop off 

 thongh in some cases they disappear before this stage is reached. 

 The youugest Argiope I bave seeu is represented in fig. 31. Here the 

 niimber of tentacles has iucreased to twelve , the head «segment« has 

 disappeared and with it the eyespots, two lateral diverticula of the sto- 

 mach bave appeared to form the liver, the body cavity is stili entirely 

 filled up by the viscera, the shells bave already attained a considerable 

 size and are pierced by aboiit twenty canals. The lophophore has stili 

 the form of a complete circle, the median indentatiou has not yet ap- 

 peared, the tentacles ali point to the centre of the circle. The mouth ap- 

 pears by an invagination. The later stages are unimportant. 



From this description it will be seen that there is in Argiope no 

 median dorsal teutacle such as Brooks ^ has described in the Deve- 

 lopment of Lingula. 



Since the view that Brachiopoda must be classed with Molluscs, 

 has been abandoued we bave had four views put forward upou the af- 

 finities of this class. Morse2 and Kowalevsky bave independantly main- 

 tained that Brachiopoda form an order of Vermes closely allied to the 

 Chaetopoda. Brooks has adopted the view which was put forward by 

 Huxley and Hancock of the relation between Brachiopoda and Polyzoa, 

 and he considers the latter to possess points of resemblance with the 

 Veliger larva of Molluscs. Van Bemmelen has urged, partly upon histo- 

 logical groimds their relationship with Chaetognatha. Finally Caldwell^ 

 in a very suggestive paper appears to class Polyzoa and Brachiopoda 

 with Phoronis, and he publishes two diag-rams which representthe body 

 pian of these three forms. 



Morse has given in parallel columns a list of the resemblances 

 existing between Brachiopods and Chaetopods, butas Brooks has already 

 pointed out, mauy of these points of resemblance are superficial while 

 the remainder apply equally to other classes such as Molluscs , Echino- 

 derms, Ascidians. 



Kowalevsky's chief arguments for placing Brachiopoda among the 

 Vermes, is the so-called segmenta tion of the larva, and the presence 



1 Ou the Development of Lingula. Chesapeake Zoological Laboratoiy. 

 Scientific; Results of the Session 1S78. Baltimore. —Also: Archives de Zoologie 

 Expéi-imentale et Generale. T. Vili. 1879— ISSO. 



- On the systematic Position of the Brachiopoda. Boston 1873. 



3 Preliminary Note on the Structure , Development , and Affinitìes of Phoro- 

 nis. Proc. of the Royal Society. !S'=«2. 



