The Microscope. 165 



Following the pilidium stage in the groups of Brachiopods, 

 Chsetopods and Bryozoa is one which we may call the mitraria stage. 

 It is thought to be assumed, possibly in a modified form but with 

 certain general featu.res which are characteristic, by the young of 

 certain genera of each of the three groups mentioned. 



It is the opinion of the author that while the beautiful Mitraria- 

 like larva here figured has many secondary characters which are 

 not ancestral for the Bryozoa, Chsetopoda and Brachiopoda, it also 

 has features which are phylogenetic for the three groups. Con- 

 sidering, then, the Pilidium as a stage following the gastrula, the 

 next stage in these groups may not be unlike the Mitraria. This 

 stage, which may be looked upon as a common one in the three 

 groups named, adds to the gastrula, among other features, the 

 following: 1. An apical tuft of cilia mounted upon an epiblastic 

 thickening; 2. A mouth surrounded by a ciliated rim; 3. A protuber- 

 ance near the mouth from which arise embryonic setre. 



While undoubtedly some of the characters of the Mitraria 

 indicated above are secondary and special adaptations of limited 

 distribution, it is believed that the majority are ancestral for 

 Brachiopods, Bryozoa and Chaetopods, and that the common ancestor 

 of these three groups is most closely preserved to us in the genus 

 Mitraria. I therefore suggest as a name for the common ancestor 

 of the Brachiopods, Chsetopods and Bryozoa, that of Mitraria 

 which up to the present is applied simply to the larval form of a 

 single genus of Chsetopoda. 



Museum of Comparative Zoology, Cambridge, Mass. 



HOW TO PRODUCE HAEMOGLOBIN OR H^MATO- 

 CRYSTALLIN. 



DR. S. WATERMAN. 

 [plate VII.] 



T3EF0RE we proceed to consider the various agents by and 

 -'-' through which blood is altered, and its optic appearances 

 presented when thus altered, it seems to me of great importance to 

 state how the hsemato-crystallin can be obtained. To this part of 

 our essay I call your most concentrated attention. We have already 

 stated, that these crystals are not found preformed in the blood, but 

 are conjugated to an alkali, most probably to the carbonate of 

 potassium. To obtain them, therefore, this combination must be 

 first broken up, or disassociated. 



