To complement mattm's answer, Kano elaborates slightly on the other schools he may have studied in another quote:

I first studied Tenjin Shinyo-ryu jujutsu With Fukuda Hachinosuke. After his death, I continued my studies with Iso Masatomo in the same school ofj ujutsu, and after his death I learned Kito-ryu from Iikubo Tsunetoshi. I subsequently studied all the other schools.

• Mind Over Muscle: Writings from the Founder of Judo, Kano Jigoro

As for what these schools were, a quote from a few paragraphs earlier appears to shed some light:

Prior to the Meiji era the schools of jujutsu numbered as many as a hundred, but among these only Kito-ryu, Kyushin-ryu, Sekiguchi-ryu, Shibukawa-ryu, Yoshin-ryu, Shin no Shinto-ryu, Tenjin Shinyo-ryu, Yagyu-ryu, and Takenouchi-ryu were widely practiced. The others were limited to only a few practitioners.

To complement mattm's answer, Kano elaborates slightly on the other schools he may have studied in another quote:

I first studied Tenjin Shinyo-ryu jujutsu With Fukuda Hachinosuke. After his death, I continued my studies with Iso Masatomo in the same school ofj ujutsu, and after his death I learned Kito-ryu from Iikubo Tsunetoshi. I subsequently studied all the other schools.

• Mind Over Muscle: Writings from the Founder of Judo, Kano Jigoro

As for what these schools were, a quote from a few paragraphs earlier appears to shed some light:

Prior to the Meiji era the schools of jujutsu numbered as many as a hundred, but among these only

• Kito-ryu

• Kyushin-ryu
• Sekiguchi-ryu
• Shibukawa-ryu
• Yoshin-ryu
• Shin no Shinto-ryu
• Tenjin Shinyo-ryu
• Yagyu-ryu
• Takenouchi-ryu

were widely practiced. The others were limited to only a few practitioners.