152 ZOOLOGY. 
authors), or away from the perpendicular end (D), and is 
surrounded by a few ciliated cirri, which forcibly recall cer- 
tain Polyzoa. The stomach and intestine form a simple 
chamber, alternating in their contractions and forcing the 
particles of food from one portion to the other.” Figure 
103, E, shows a more advanced stage, in which a fold is 
seen on each side of the stomach ; from the fold is developed 
the complicated liver of the adult, as seen in EK, which 
represents the animal about an eighth of an inch long. The 
arms (lophophore) begin to assume the horseshoe-shaped. 
form of Pectinatella and other fresh-water Polyzoa. At this 
stage the mouth begins to turn towards the dorsal valve, and 
as the central lobes of the lophophore begin to develop, the 
lateral arms are deflected asin F. In the stage G an epis- 
tome is marked, and Morse noticed that the end of the 
5B G\er 
Fig. 103.—Later larval stages of Terebratulina.—After Morse. 
intestine was heid to the mantle by an attachment, as in the 
adult, reminding one of the funiculus in the fresh-water 
Polyzoa. In tracing the development of Argiope, Kowal- 
evsky has shown that the larva is strikingly like those of the 
Annelids, as well as the Tornaria stage of Balanoglossus. 
While in their development the Brachiopoda recall the: 
larve of the true worms, they resemble the adult worms in 
the general arrangement of the arms and viscera, though 
they lack the highly developed nervous system of the Anne- 
lids, as well as a vascular system, while the body is not 
jointed. On the other hand they are closely related to the 
Polyzoa, and it seems probable that the Brachiopods and 
Polyzoa were derived from common low vermian ancestors, 
while the true Annelids probably sprang independently 
from a higher ancestry. They are also a generalized type, 
