TilK Ii!-:\ Kl.nl'MKAT OK Tlrtf BRACHloI'. >f > \ |n] 



The nervous system of the articulated Brachiopods, in 

 which it has been best made out, consists of a relatively thick 

 gaiiirliomc band on the ventral side of the mouth, the ends of 

 which are united by a commissural cord, which surrounds the 

 gullet, and bears two small ganglionic enlargements. The hit- 

 ter probably answer to the cerebral, the former to the pedal, 

 ganglia of the Lauiellibranchiata. Immediately behind the 

 pedal mass, from which two large nerves to the dorsal or ante- 

 rior lobe of the mantle are given off, are two elongated ganglia, 

 cmmcrtcd by a commissure of their own, which possibly 

 respond with the parieto-splanchriic ganglia of the higher M<>1- 

 lu>ks. The nerves to the ventral lobe of the mantle and those 

 to the peduncle arise from these ganglia. 



In the inarticulated Brachiopods, our knowledge of the ner- 

 vous system is very imperfect. In Mmjnln, Professor Owen 

 has described two lateral nerve-cords, and the observation 

 has been confirmed by Gratiolet and Morse. The latter anato- 

 mist finds similar cords in Distinct, and Gratiolet has de- 

 scribed an cesophageal ring in Lin(/u/<i. 1 



The reproductive organs are lodged in the perivisceral 

 cavity or its prolongations, and are apparently always con- 

 tained in processes of the lining membrane of that cavity. 

 It is not clear whether hermaphrodism is the rule or the ex- 

 ception. Thecidium, however, has been shown by Lacaze- 

 Duthiers to be dioecious ; and, according to Morse, the sexes 

 are distinct in Terebratulina and Distino. 



Th; development of the Brachiopoda, notwithstanding 

 the important observations of F. Mailer, 2 Lacaze-Duthiers, 8 

 and especially of Morse, 4 stood much in need of further eluci- 

 dation (especially in regard to the earlier conditions of the 

 embryo), until quite recently, when the investigations of 

 Kowalewsky 5 filled up the hiatus in our knowledge for the 

 genera Ar<fiope, Thecidium, Terebratula, and Terebratrdin<;. 

 The egg becomes converted into a vesicular morula, in which 

 an alimentary sac is developed by in vagi nation, and this sac 

 gives off, as in Sagitta, two diverticula, which become shut 



1 "Recherches pour servir a 1'histoire des Rrachiopodes." ("Journal de 

 Conohyliologie." 1860.) 



Ki-sehivil>imir einer Brachiopoclen-Larva." (" Archiv fur Anat," 1860.) 



a " Histoire de la Thccidt'e." (" Ann. d'Hist. Nat.," 1861.) 



4 " On the earlv stages of 7Vwfiw//^///,i' .sv/./, ntrlitnui:*." ( u Memoirs of the 

 Hoston Sociftv of Natural History." 1*W. and the memoir already cited). 



Contained in a memoir, published at Mo^-o\v in 1874, for which I am in- 

 dt'htt^l to tlu> courtesy of the author. It is in Kussian : luit I have lieen al>le to 

 acquaint myself with its contents, to some extent, by the aid of a friend. 



